Thermally reversible color forming composition and thermally reversible recording medium using the thermally reversible color forming composition

ABSTRACT

A thermally reversible color forming composition which includes an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein the electron-accepting compound is a carboxylic acid compound having the following general formula (1): 
     
         R.sub.1 --X--R.sub.2 --COOH                                (1) 
    
     in which, X represents a divalent group having at least one hetero atom, R 1  represents a hydrocarbon group having at least one hetero atom, R 2  represents an aliphatic hydrocarbon group, which may be substituted and whose principle chain contains less than 6 carbon atoms.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermally reversible color forming composition and a thermally reversible recording medium using the thermally reversible color forming composition. More particularly, the present invention relates to thermally reversible color forming compositions which involves a color forming reaction between an electron-donating chromophoric compound and an electron-accepting compound, and thermally reversible recording media using the thermally reversible color forming composition, by which a formation and a deletion of an image may be carried out by adjusting thermal energy applied to the composition.

2. Description of the Related Art

Thermal recording media which use a color producing reaction between an electron-donating chromophoric compound (hereinafter also referred to as a "color-producing agent" or "leuco dye") and an electron-accepting compound (hereinafter also referred to as a "color developer") in a recording layer is well known in the art. These recording media are generally used for a printer of a facsimile, a word processor, a scientific instrument and so on.

However, all of the conventional recording media which are practically used are non-reversible type recording media. That is, once a color is produced on the recording medium, it is non-reversibly fixed on the medium. Therefore, it is not possible to delete an image picture on the medium and to use the medium repeatedly.

On the other hand, a thermally reversible recording medium which can perform a reversible formation and a deletion of a colored image is disclosed in Japanese Laid-Open Patent Application No.60-193691 in which a combination of gallic acid and fluoroglucinol is used as the color developer, Japanese Laid-Open Patent Application No.61-237684 in which compounds such as phenol phthalene and thymol phthalene are used as the color developer, Japanese Laid-Open Patent Application Nos.62-138556, 62-138568 and 62-140881 in which a homogeneous mixture of a color-producing agent, a color developer and a carboxylate is contained in a recording layer, Japanese Laid-Open Patent Application No.63-173884 in which a derivative of ascorbic acid is used as a color developer, and Japanese Laid-Open Patent Application Nos.2-188293 and 2-18294 in which a salt of bis(hydroxyphenyl) acetic acid or gallic acid with higher aliphatic amine is used as a color developer.

However, these conventional thermally reversible recording media have problems such as compatibility in color-producing stability and color deletion ability, sufficient concentration of produced colors, and stability when used repeatedly. Therefore, these thermally reversible media are generally not suitable for practical use.

It is disclosed, in Japanese Laid-Open Patent Application No.5-124360, a thermally reversible color forming composition comprising an organic phosphate compound having a long-chain aliphatic hydrocarbon group, an aliphatic carboxylic acid or a phenol compound as a color developer and a leuco dye as a color producing agent. By using the above composition, it is possible to carry out a formation and deletion of colors relatively easily, and a stability of such formation and deletion of colors may be maintained during repeated use. In the above Patent Application No.5-124360, a thermally reversible recording medium using the thermally reversible color forming composition in a recording layer is also disclosed. The recording medium has an advantage, compared with other conventional recording media, in that an excellent stability of color formation, color deletion, and a concentration of produced colors may be achieved. However, its color deletion rate is rather slow for practical use. Thus, development of thermally reversible recording medium in which a colored image once formed can be deleted at a practically sufficient speed and yet provide stability so that colors can be maintained is desired.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to provide a thermally reversible color forming composition and a thermally reversible recording medium using the thermally reversible color forming composition.

A more specific object of the present invention is to provide a thermally reversible color forming composition and a thermally reversible recording medium using the thermally reversible color forming composition, by which a stability in color formation and color deletion may be maintained, and a sufficient deletion speed of a colored image may be attained.

It is another object of the present invention to provide a thermally reversible color forming composition involving a color forming reaction between an electron-donating chromophoric compound and an electron-accepting compound, and a thermally reversible recording medium using the thermally reversible color forming composition, by which a formation and a deletion of an image may be carried out by adjusting thermal energy applied to the composition.

The objects described above are achieved by a thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which a color may be formed and deleted depending on at least one of a temperature for the thermally reversible color forming composition and a cooling rate for the thermally reversible color forming composition after heating the thermally reversible color forming composition, wherein a carboxylic acid compound having the following general formula:

    R.sub.1 --X--R.sub.2 --COOH

(wherein, X represents a divalent group having at least one hetero atom,

R₁ represents a hydrocarbon group which may be substituted and

R₂ represents an aliphatic hydrocarbon group, which may be substituted and whose principle chain containing less than 6 carbon atoms) is used as the electron-accepting compound.

The objects described above are also achieved by the thermally reversible color forming composition, wherein R₁ is substituted by a substituent selected from a group consisting of a hydroxy group, halogens and alkoxy groups.

The objects described above are also achieved by the thermally reversible color forming composition, wherein R₂ is substituted by a substituent selected from a group consisting of a hydroxy group and halogens.

The objects described above are also achieved by the thermally reversible color forming composition, wherein R₁ is substituted by a substituent selected from a group consisting of a hydroxy group, halogens and alkoxy groups and R₂ is substituted by a substituent selected from a group consisting of a hydroxy group and halogens.

The objects described above are also achieved by the thermally reversible color forming composition, wherein the carboxylic acid compound has the following general formula:

    CH.sub.3 (CH.sub.2).sub.m-1 --X--(CH.sub.2).sub.n --COOH

wherein m represents an integer between 8 and 22 and n represents an integer between 0 and 6.

The objects described above are also achieved by the thermally reversible color forming composition, wherein the --X-- in the formula of the carboxylic acid compound may be expressed as:

    --Y--(R.sub.3 --Y').sub.r --

wherein Y and Y' represents, respectively, a divalent group having at least one hetero atom,

R₃ represents a divalent hydrocarbon group whose principle chain may contain a non-limiting number of carbon atoms, a portion of which may form aromatic ring(s), and

_(r) represents an integer between 1 and 4, and when _(r) is more than 2, R₃ and Y', respectively, may be the same or different.

The objects described above are also achieved by the thermally reversible color forming composition, wherein the carboxylic acid compound has a general formula selected from the group consisting of following:

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.2 --COOH

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.2 --COOH

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.2 --COOH,

and

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.3 "'--Y""--R.sub.2 --COOH

wherein R₃ ', R₃ " and R₃ "', respectively, has the same definition as R₃ and they may be one of the same and different from each other, and

Y", Y"' and Y"" has the same definition as Y, and they may be one of the same and different from each other.

According to the above thermally reversible color forming compositions, a stability in color formation and color deletion may be maintained even after repeated use, and a practically sufficient deletion speed of an colored image may be obtained.

The objects described above are also achieved by a thermally reversible recording medium comprising a supporting layer and a recording layer formed on the supporting layer, wherein the recording layer is comprised, as a main component, of a thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which a color may be formed and deleted depending on at least one of a temperature for the thermally reversible color forming composition and a cooling rate for the thermally reversible color forming composition after heating the thermally reversible color forming composition, wherein a carboxylic acid compound having the following general formula:

    R.sub.1 --X--R.sub.2 --COOH

(wherein X represents a divalent group having at least one hetero atom,

R₁ represents a hydrocarbon group which may be substituted and

R₂ represents an aliphatic hydrocarbon group, which may be substituted and whose principle chain containing less than 6 carbon atoms) is used as the electron-accepting compound.

The objects described above are also achieved by the thermally reversible recording medium, wherein the carboxylic acid compound has the following general formula:

    CH.sub.3 (CH.sub.2).sub.m-1 --X--(CH.sub.2).sub.n --COOH

wherein m represents an integer between 8 and 22 and n represents an integer between 0 and 6.

The objects described above are also achieved by the thermally reversible recording medium, wherein the --X-- in the formula of the carboxylic acid compound may be expressed as:

    --Y--(R.sub.3 --Y').sub.r --

wherein Y and Y' represents, respectively, a divalent group having at least one hetero atom,

R₃ represents a divalent hydrocarbon group whose principle chain may contain a non-limiting number of carbon atoms, a portion of which may form aromatic ring(s), and

_(r) represents an integer between 1 and 4, and when _(r) is more than 2, R₃ and Y', respectively, may be the same or different.

The objects described above are also achieved by the thermally reversible recording medium as claimed in claim 10, wherein the carboxylic acid compound has a general formula selected from the group consisting of following:

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.2 --COOH

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.2 --COOH

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.2 --COOH,

and

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.3 "'--Y""--R.sub.2 --COOH

wherein R₃ ', R₃ " and R₃ "', respectively, have the same definition as R₃ and they may be one of the same and different from each other, and

Y", Y"' and Y"" has the same definition as Y, and they may be one of the same and different from each other.

According to the above thermally reversible recording medium, a stability in color formation and color deletion may be maintained even after repeated use, and a practically sufficient deletion speed of an colored image may be obtained. Also, the thermally reversible recording medium has a high contrast and a high durability which is sufficient to be a practical excellent thermally reversible recording medium.

Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanied drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a color formation/deletion characteristics of a thermally reversible color forming composition according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A thermally reversible color forming composition and a recording medium using the composition according to the present invention will be described in detail hereinafter.

The inventors of the present invention have made a discovery that a balance between the color developing ability of a color developer having a long chain aliphatic group for a color producing agent and a cohesive force among molecules is very important for a reversible color-forming and color-deleting phenomenon caused by a composition comprising a color producing agent and a color developer. Based on this finding, various kinds of compounds were examined and, as a result, it was found that the above-mentioned problems associated with the conventional thermally reversible color forming compositions and thermally reversible recording media using the compositions may be solved by using a carboxylic acid compound having a certain structure as the electron-donating compound.

According to the present invention, a carboxylic acid compound having the following general formula (1):

    R.sub.1 --X--R.sub.2 --COOH                                (1)

(wherein X represents a divalent group having at least one hetero atom,

R₁ represents a hydrocarbon group which may be unsubstituted or substituted and

R₂ represents an aliphatic hydrocarbon group, which may be unsubstituted or substituted and whose principle chain containing less than 6 carbon atoms), is used as an electron-accepting compound for a thermally reversible color forming composition. According to the present invention, a colored image is produced by a reversible coloration reaction between the electron-accepting compound and an electron-donating chromophoric compound.

Now, the above-mentioned carboxylic acid compound having the formula (1) will be described in detail.

As described above, R₁ represents a hydrocarbon group which may be unsubstituted or substituted by a substituent. R₁ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group or may be a hydrocarbon group comprising both the aromatic moiety and the aliphatic moiety. Also, the aliphatic hydrocarbon group may be of a straight chain or may be branched, and can contain unsaturated bonds. Examples of a typical substituent for the hydrocarbon group include a hydroxy group, halogens, alkoxy groups and so on.

Further, since the stability in a color formation and a color deletion ability of the composition according to the present invention will be decreased if R₁ contains less than 7 carbon atoms, it is preferable that R₁ contains more than 8 carbon atoms and it is more preferable that R₁ contains more than 11 carbon atoms.

Preferable examples of R₁ include: ##STR1## wherein p, p', p" and p"', respectively, preferably represents an integer which satisfies the above mentioned number of carbons for R₁.

R₂ represents an aliphatic hydrocarbon group, which may be unsubstituted or substituted and whose principle chain contains less than 6 carbon atoms. The aliphatic hydrocarbon group may be of a straight chain or may be branched, and can contain unsaturated bonds. Examples of a typical substituent for the hydrocarbon group include a hydroxy group, halogens and so on.

Also, since the color producing ability of the composition according to the present invention will be decreased if R₂ contains more than 7 carbon atoms, it is preferable that R₂ contains less than 6 carbon atoms.

Preferable examples of R₂ include: ##STR2## wherein q and p', respectively, preferably represents an integer which satisfies the above mentioned number of carbons for R₂, and q" and q"', represents an integer which is not particularly limited but preferable less than 5.

X represents a divalent group having at least one hetero atom. Non-limiting examples of X, according to the present invention, include: ##STR3##

Examples of preferable carboxylic acid compound having the above formula (1) according to the present invention include a compound having the following formula (2):

    CH.sub.3 (CH.sub.2).sub.m-1 --X--(CH.sub.2).sub.n --COOH   (2)

wherein m represents an integer between 8 and 22 and n represents an integer between 0 and 6.

Examples of carboxylic acid compound having the above formula (1) according to the present invention are shown in the following Tables 1-1 through 1-14. However, they are not by any means to restrict the present invention.

                  TABLE 1     ______________________________________     Compound No.              CH.sub.3 (CH.sub.2).sub.m-1 --                          --X--         --(CH.sub.2).sub.n --     ______________________________________     1        CH.sub.3 (CH.sub.2).sub.7 --                          --NHCO--      --CH.sub.2 --     2        CH.sub.3 (CH.sub.2).sub.11 --                          --NHCO--      --CH.sub.2 --     3        CH.sub.3 (CH.sub.2).sub.13 --                          --NHCO--      --CH.sub.2 --     4        CH.sub.3 (CH.sub.2).sub.15 --                          --NHCO--      --CH.sub.2 --     5        CH.sub.3 (CH.sub.2).sub.17 --                          --NHCO--      --CH.sub.2 --     6        CH.sub.3 (CH.sub.2).sub.19 --                          --NHCO--      --CH.sub.2 --     7        CH.sub.3 (CH.sub.2).sub.21 --                          --NHCO--      --CH.sub.2 --     8        CH.sub.3 (CH.sub.2).sub.7 --                          --NHCO--      --(CH.sub.2).sub.2 --     9        CH.sub.3 (CH.sub.2).sub.11 --                          --NHCO--      --(CH.sub.2).sub.2 --     10       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCO--      --(CH.sub.2).sub.2 --     11       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCO--      --(CH.sub.2).sub.2 --     12       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCO--      --(CH.sub.2).sub.2 --     13       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCO--      --(CH.sub.2).sub.2 --     14       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCO--      --(CH.sub.2).sub.2 --     15       CH.sub.3 (CH.sub.2).sub.7 --                          --NHCO--      --(CH.sub.2).sub.3 --     16       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCO--      --(CH.sub.2).sub.3 --     17       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCO--      --(CH.sub.2).sub.3 --     18       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCO--      --(CH.sub.2).sub.3 --     19       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCO--      --(CH.sub.2).sub.3 --     20       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCO--      --(CH.sub.2).sub.3 --     21       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCO--      --(CH.sub.2).sub.3 --     22       CH.sub.3 (CH.sub.2).sub.7 --                          --NHCO--      --(CH.sub.2).sub.4 --     23       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCO--      --(CH.sub.2).sub.4 --     24       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCO--      --(CH.sub.2).sub.4 --     25       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCO--      --(CH.sub.2).sub.4 --     26       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCO--      --(CH.sub.2).sub.4 --     27       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCO--      --(CH.sub.2).sub.4 --     28       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCO--      --(CH.sub.2).sub.4 --     29       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCO--      --(CH.sub.2).sub.5 --     30       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCO--      --(CH.sub.2).sub.5 --     31       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCO--      --(CH.sub.2).sub.5 --     32       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCO--      --(CH.sub.2).sub.5 --     33       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCO--      --(CH.sub.2).sub.6 --     34       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCO--      --(CH.sub.2).sub.6 --     35       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCO--      --(CH.sub.2).sub.6 --     36       CH.sub.3 (CH.sub.2).sub.7 --                          --NHCONH--    --CH.sub.2 --     37       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONH--    --CH.sub.2 --     38       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONH--    --CH.sub.2 --     39       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONH--    --CH.sub.2 --     40       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONH--    --CH.sub.2 --     41       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCONH--    --CH.sub.2 --     42       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCONH--    --CH.sub.2 --     43       CH.sub.3 (CH.sub.2).sub.7 --                          --NHCONH--    --(CH.sub.2).sub.2 --     44       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONH--    --(CH.sub.2).sub.2 --     45       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONH--    --(CH.sub.2).sub.2 --     46       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONH--    --(CH.sub.2).sub.2 --     47       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONH--    --(CH.sub.2).sub.2 --     48       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCONH--    --(CH.sub.2).sub.2 --     49       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCONH--    --(CH.sub.2).sub.2 --     50       CH.sub.3 (CH.sub.2).sub.7 --                          --NHCONH--    --(CH.sub.2).sub.3 --     51       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONH--    --(CH.sub.2).sub.3 --     52       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONH--    --(CH.sub.2).sub.3 --     53       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONH--    --(CH.sub.2).sub.3 --     54       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONH--    --(CH.sub.2).sub.3 --     55       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCONH--    --(CH.sub.2).sub.3 --     56       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCONH--    --(CH.sub.2).sub.3 --     57       CH.sub.3 (CH.sub.2).sub.7 --                          --NHCONH--    --(CH.sub.2).sub.4 --     58       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONH--    --(CH.sub.2).sub.4 --     59       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONH--    --(CH.sub.2).sub.4 --     60       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONH--    --(CH.sub.2).sub.4 --     61       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONH--    --(CH.sub.2).sub.4 --     62       CH.sub.3 (CH.sub.2).sub.19 --                          --NHCONH--    --(CH.sub.2).sub.4 --     63       CH.sub.3 (CH.sub.2).sub.21 --                          --NHCONH--    --(CH.sub.2).sub.4 --     64       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONH--    --(CH.sub.2).sub.5 --     65       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONH--    --(CH.sub.2).sub.5 --     66       CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONH--    --(CH.sub.2).sub.5 --     67       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONH--    --(CH.sub.2).sub.5 --     68       CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONH--    --(CH.sub.2).sub.6 --     69       CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONH--    --(CH.sub.2).sub.6 --     70       CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONH--    --(CH.sub.2).sub.6 --     71       CH.sub.3 (CH.sub.2).sub.7 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     72       CH.sub.3 (CH.sub.2).sub.11 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     73       CH.sub.3 (CH.sub.2).sub.13 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     74       CH.sub.3 (CH.sub.2).sub.15 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     75       CH.sub.3 (CH.sub.2).sub.17 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     76       CH.sub.3 (CH.sub.2).sub.19 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     77       CH.sub.3 (CH.sub.2).sub.21 --                          --NHSO.sub.2 --                                        --CH.sub.2 --     78       CH.sub.3 (CH.sub.2).sub.7 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     79       CH.sub.3 (CH.sub.2).sub.11 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     80       CH.sub.3 (CH.sub.2).sub.13 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     81       CH.sub.3 (CH.sub.2).sub.15 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     82       CH.sub.3 (CH.sub.2).sub.17 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     83       CH.sub.3 (CH.sub.2).sub.19 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     84       CH.sub.3 (CH.sub.2).sub.21 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.2 --     85       CH.sub.3 (CH.sub.2).sub.7 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     86       CH.sub.3 (CH.sub.2).sub.11 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     87       CH.sub.3 (CH.sub.2).sub.13 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     88       CH.sub.3 (CH.sub.2).sub.15 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     89       CH.sub.3 (CH.sub.2).sub.17 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     90       CH.sub.3 (CH.sub.2).sub.19 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     91       CH.sub.3 (CH.sub.2).sub.21 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.3 --     92       CH.sub.3 (CH.sub.2).sub.7 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     93       CH.sub.3 (CH.sub.2).sub.11 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     94       CH.sub.3 (CH.sub.2).sub.13 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     95       CH.sub.3 (CH.sub.2).sub.15 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     96       CH.sub.3 (CH.sub.2).sub.17 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     97       CH.sub.3 (CH.sub.2).sub.19 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     98       CH.sub.3 (CH.sub.2).sub.21 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.4 --     99       CH.sub.3 (CH.sub.2).sub.11 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.5 --     100      CH.sub.3 (CH.sub.2).sub.13 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.5 --     101      CH.sub.3 (CH.sub.2).sub.15 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.5 --     102      CH.sub.3 (CH.sub.2).sub.17 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.5 --     103      CH.sub.3 (CH.sub.2).sub.11 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.6 --     104      CH.sub.3 (CH.sub.2).sub.13 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.6 --     105      CH.sub.3 (CH.sub.2).sub.17 --                          --NHSO.sub.2 --                                        --(CH.sub.2).sub.6 --     106      CH.sub.3 (CH.sub.2).sub.7 --                          --NHCSNH--    --CH.sub.2 --     107      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCSNH--    --CH.sub.2 --     108      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCSNH--    --CH.sub.2 --     109      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCSNH--    --CH.sub.2 --     110      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCSNH--    --CH.sub.2 --     111      CH.sub.3 (CH.sub.2).sub.19 --                          --NHCSNH--    --CH.sub.2 --     112      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCSNH--    --CH.sub.2 --     113      CH.sub.3 (CH.sub.2).sub.7 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     114      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     115      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     116      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     117      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     118      CH.sub.3 (CH.sub.2).sub.19 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     119      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCSNH--    --(CH.sub.2).sub.2 --     120      CH.sub.3 (CH.sub.2).sub.7 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     121      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     122      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     123      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     124      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     125      CH.sub.3 (CH.sub.2).sub.19 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     126      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCSNH--    --(CH.sub.2).sub.3 --     127      CH.sub.3 (CH.sub.2).sub.7 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     128      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     129      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     130      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     131      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     132      CH.sub.3 (CH.sub.2).sub.19 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     133      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCSNH--    --(CH.sub.2).sub.4 --     134      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCSNH--    --(CH.sub.2).sub.5 --     135      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCSNH--    --(CH.sub.2).sub.5 --     136      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCSNH--    --(CH.sub.2).sub.5 --     137      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCSNH--    --(CH.sub.2).sub.5 --     138      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCSNH--    --(CH.sub.2).sub.6 --     139      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCSNH--    --(CH.sub.2).sub.6 --     140      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCSNH--    --(CH.sub.2).sub.6 --     141      CH.sub.3 (CH.sub.2).sub.12 --                          --CONH--      --CH.sub.2 --     142      CH.sub.3 (CH.sub.2).sub.14 --                          --CONH--      --CH.sub.2 --     143      CH.sub.3 (CH.sub.2).sub.16 --                          --CONH--      --CH.sub.2 --     144      CH.sub.3 (CH.sub.2).sub.20 --                          --CONH--      --CH.sub.2 --     145      CH.sub.3 (CH.sub.2).sub.12 --                          --CONH--      --(CH.sub.2).sub.2 --     146      CH.sub.3 (CH.sub.2).sub.14 --                          --CONH--      --(CH.sub.2).sub.2 --     147      CH.sub.3 (CH.sub.2).sub.16 --                          --CONH--      --(CH.sub.2).sub.2 --     148      CH.sub.3 (CH.sub.2).sub.20 --                          --CONH--      --(CH.sub.2).sub.2 --     149      CH.sub.3 (CH.sub.2).sub.12 --                          --CONH--      --(CH.sub.2).sub.3 --     150      CH.sub.3 (CH.sub.2).sub.14 --                          --CONH--      --(CH.sub.2).sub.3 --     151      CH.sub.3 (CH.sub.2).sub.16 --                          --CONH--      --(CH.sub.2).sub.3 --     152      CH.sub.3 (CH.sub.2).sub.20 --                          --CONH--      --(CH.sub.2).sub.3 --     153      CH.sub.3 (CH.sub.2).sub.12 --                          --CONH--      --(CH.sub.2).sub.4 --     154      CH.sub.3 (CH.sub.2).sub.14 --                          --CONH--      --(CH.sub.2).sub.4 --     155      CH.sub.3 (CH.sub.2).sub.16 --                          --CONH--      --(CH.sub.2).sub.4 --     156      CH.sub.3 (CH.sub.2).sub.20 --                          --CONH--      --(CH.sub.2).sub.4 --     157      CH.sub.3 (CH.sub.2).sub.12 --                          --CONH--      --(CH.sub.2).sub.5 --     158      CH.sub.3 (CH.sub.2).sub.16 --                          --CONH--      --(CH.sub.2).sub.5 --     159      CH.sub.3 (CH.sub.2).sub.16 --                          --CONH--      --(CH.sub.2).sub.6 --     160      CH.sub.3 (CH.sub.2).sub.14 --                          --COO--       --CH.sub.2 --     161      CH.sub.3 (CH.sub.2).sub.16 --                          --COO--       --CH.sub.2 --     162      CH.sub.3 (CH.sub.2).sub.20 --                          --COO--       --CH.sub.2 --     163      CH.sub.3 (CH.sub.2).sub.12 --                          --COO--       --(CH.sub.2).sub.2 --     164      CH.sub.3 (CH.sub.2).sub.14 --                          --COO--       --(CH.sub.2).sub.2 --     165      CH.sub.3 (CH.sub.2).sub.16 --                          --COO--       --(CH.sub.2).sub.2 --     166      CH.sub.3 (CH.sub.2).sub.14 --                          --COO--       --(CH.sub.2).sub.3 --     167      CH.sub.3 (CH.sub.2).sub.16 --                          --COO--       --(CH.sub.2).sub.3 --     168      CH.sub.3 (CH.sub.2).sub.20 --                          --COO--       --(CH.sub.2).sub.3 --     169      CH.sub.3 (CH.sub.2).sub.12 --                          --COO--       --(CH.sub.2).sub.4 --     170      CH.sub.3 (CH.sub.2).sub.14 --                          --COO--       --(CH.sub.2).sub.4 --     171      CH.sub.3 (CH.sub.2).sub.16 --                          --COO--       --(CH.sub.2).sub.4 --     172      CH.sub.3 (CH.sub.2).sub.14 --                          --COO--       --(CH.sub.2).sub.5 --     173      CH.sub.3 (CH.sub.2).sub.16 --                          --COO--       --(CH.sub.2).sub.5 --     174      CH.sub.3 (CH.sub.2).sub.14 --                          --COO--       --(CH.sub.2).sub.6 --     175      CH.sub.3 (CH.sub.2).sub.16 --                          --COO--       --(CH.sub.2).sub.6 --     176      CH.sub.3 (CH.sub.2).sub.12 --                          --CONHCO--    --CH.sub.2 --     177      CH.sub.3 (CH.sub.2).sub.14 --                          --CONHCO--    --CH.sub.2 --     178      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCO--    --CH.sub.2 --     179      CH.sub.3 (CH.sub.2).sub.20 --                          --CONHCO--    --CH.sub.2 --     180      CH.sub.3 (CH.sub.2).sub.12 --                          --CONHCO--    --(CH.sub.2).sub.2 --     181      CH.sub.3 (CH.sub.2).sub.14 --                          --CONHCO--    --(CH.sub.2).sub.2 --     182      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCO--    --(CH.sub.2).sub.2 --     183      CH.sub.3 (CH.sub.2).sub.20 --                          --CONHCO--    --(CH.sub.2).sub.2 --     184      CH.sub.3 (CH.sub.2).sub.12 --                          --CONHCO--    --(CH.sub.2).sub.3 --     185      CH.sub.3 (CH.sub.2).sub.14 --                          --CONHCO--    --(CH.sub.2).sub.3 --     186      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCO--    --(CH.sub.2).sub.3 --     187      CH.sub.3 (CH.sub.2).sub.20 --                          --CONHCO--    --(CH.sub.2).sub.3 --     188      CH.sub.3 (CH.sub.2).sub.12 --                          --CONHCO--    --(CH.sub.2).sub.4 --     189      CH.sub.3 (CH.sub.2).sub.14 --                          --CONHCO--    --(CH.sub.2).sub.4 --     190      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCO--    --(CH.sub.2).sub.4 --     191      CH.sub.3 (CH.sub.2).sub.20 --                          --CONHCO--    --(CH.sub.2).sub.4 --     192      CH.sub.3 (CH.sub.2).sub.12 --                          --CONHCO--    --(CH.sub.2).sub.5 --     193      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCO--    --(CH.sub.2).sub.5 --     194      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCO--    --(CH.sub.2).sub.6 --     195      CH.sub.3 (CH.sub.2).sub.14 --                          --COS--       --CH.sub.2 --     196      CH.sub.3 (CH.sub.2).sub.16 --                          --COS--       --CH.sub.2 --     197      CH.sub.3 (CH.sub.2).sub.20 --                          --COS--       --CH.sub.2 --     198      CH.sub.3 (CH.sub.2).sub.12 --                          --COS--       --(CH.sub.2).sub.2 --     199      CH.sub.3 (CH.sub.2).sub.14 --                          --COS--       --(CH.sub.2).sub.2 --     200      CH.sub.3 (CH.sub.2).sub.16 --                          --COS--       --(CH.sub.2).sub.2 --     201      CH.sub.3 (CH.sub.2).sub.14 --                          --COS--       --(CH.sub.2).sub.3 --     202      CH.sub.3 (CH.sub.2).sub.16 --                          --COS--       --(CH.sub.2).sub.3 --     203      CH.sub.3 (CH.sub.2).sub.20 --                          --COS--       --(CH.sub.2).sub.3 --     204      CH.sub.3 (CH.sub.2).sub.12 --                          --COS--       --(CH.sub.2).sub.4 --     205      CH.sub.3 (CH.sub.2).sub.14 --                          --COS--       --(CH.sub.2).sub.4 --     206      CH.sub.3 (CH.sub.2).sub.16 --                          --COS--       --(CH.sub.2).sub.4 --     207      CH.sub.3 (CH.sub.2).sub.14 --                          --COS--       --(CH.sub.2).sub.5 --     208      CH.sub.3 (CH.sub.2).sub.16 --                          --COS--       --(CH.sub.2).sub.5 --     209      CH.sub.3 (CH.sub.2).sub.14 --                          --COS--       --(CH.sub.2).sub.6 --     210      CH.sub.3 (CH.sub.2).sub.16 --                          --COS--       --(CH.sub.2).sub.6 --     211      CH.sub.3 (CH.sub.2).sub.12 --                          --CO--        --CH.sub.2 --     212      CH.sub.3 (CH.sub.2).sub.14 --                          --CO--        --CH.sub.2 --     213      CH.sub.3 (CH.sub.2).sub.16 --                          --CO--        --CH.sub.2 --     214      CH.sub.3 (CH.sub.2).sub.20 --                          --CO--        --CH.sub.2 --     215      CH.sub.3 (CH.sub.2).sub.12 --                          --CO--        --(CH.sub.2).sub.2 --     216      CH.sub.3 (CH.sub.2).sub.14 --                          --CO--        --(CH.sub.2).sub.2 --     217      CH.sub.3 (CH.sub.2).sub.16 --                          --CO--        --(CH.sub.2).sub.2 --     218      CH.sub.3 (CH.sub.2).sub.20 --                          --CO--        --(CH.sub.2).sub.2 --     219      CH.sub.3 (CH.sub.2).sub.12 --                          --CO--        --(CH.sub.2).sub.3 --     220      CH.sub.3 (CH.sub.2).sub.14 --                          --CO--        --(CH.sub.2).sub.3 --     221      CH.sub.3 (CH.sub.2).sub.16 --                          --CO--        --(CH.sub.2).sub.3 --     222      CH.sub.3 (CH.sub.2).sub.16 --                          --CO--        --(CH.sub.2).sub.4 --     223      CH.sub.3 (CH.sub.2).sub.16 --                          --CO--        --(CH.sub.2).sub.5 --     224      CH.sub.3 (CH.sub.2).sub.16 --                          --CO--        --(CH.sub.2).sub.6 --     225      CH.sub.3 (CH.sub.2).sub.12 --                          --SO.sub.2 -- --CH.sub.2 --     226      CH.sub.3 (CH.sub.2).sub.14 --                          --SO.sub.2 -- --CH.sub.2 --     227      CH.sub.3 (CH.sub.2).sub.16 --                          --SO.sub.2 -- --CH.sub.2 --     228      CH.sub.3 (CH.sub.2).sub.20 --                          --SO.sub.2 -- --CH.sub.2 --     229      CH.sub.3 (CH.sub.2).sub.12 --                          --SO.sub.2 -- --(CH.sub.2).sub.2 --     230      CH.sub.3 (CH.sub.2).sub.14 --                          --SO.sub.2 -- --(CH.sub.2).sub.2 --     231      CH.sub.3 (CH.sub.2).sub.16 --                          --SO.sub.2 -- --(CH.sub.2).sub.2 --     232      CH.sub.3 (CH.sub.2).sub.20 --                          --SO.sub.2 -- --(CH.sub.2).sub.2 --     233      CH.sub.3 (CH.sub.2).sub.12 --                          --SO.sub.2 -- --(CH.sub.2).sub.3 --     234      CH.sub.3 (CH.sub.2).sub.14 --                          --SO.sub.2 -- --(CH.sub.2).sub.3 --     235      CH.sub.3 (CH.sub.2).sub.16 --                          --SO.sub.2 -- --(CH.sub.2).sub.3 --     236      CH.sub.3 (CH.sub.2).sub.16 --                          --SO.sub.2 -- --(CH.sub.2).sub.4 --     237      CH.sub.3 (CH.sub.2).sub.16 --                          --SO.sub.2 -- --(CH.sub.2).sub.5 --     238      CH.sub.3 (CH.sub.2).sub.16 --                          --SO.sub.2 -- --(CH.sub.2).sub.6 --     239      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCONH--  --CH.sub.2 --     240      CH.sub.3 (CH.sub.2).sub.20 --                          --CONHCONH--  --CH.sub.2 --     241      CH.sub.3 (CH.sub.2).sub.14 --                          --CONHCONH--  --(CH.sub.2).sub.2 --     242      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCONH--  --(CH.sub.2).sub.2 --     243      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCONH--  --(CH.sub.2).sub.3 --     244      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCONH--  --(CH.sub.2).sub.4 --     245      CH.sub.3 (CH.sub.2).sub.16 --                          --CONHCONH--  --(CH.sub.2).sub.5 --     246      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCOO--     --CH.sub.2 --     247      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCOO--     --CH.sub.2 --     248      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOO--     --CH.sub.2 --     249      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOO--     --CH.sub.2 --     250      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCOO--     --(CH.sub.2).sub.2 --     251      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOO--     --(CH.sub.2).sub.2 --     252      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOO--     --(CH.sub.2).sub.2 --     253      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCOO--     --(CH.sub.2).sub.2 --     254      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCOO--     --(CH.sub.2).sub.3 --     255      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOO--     --(CH.sub.2).sub.3 --     256      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOO--     --(CH.sub.2).sub.3 --     257      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOO--     --(CH.sub.2).sub.4 --     258      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOO--     --(CH.sub.2).sub.5 --     259      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOO--     --(CH.sub.2).sub.6 --     260      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCOS--     --CH.sub.2 --     261      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOS--     --CH.sub.2 --     262      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOS--     --CH.sub.2 --     263      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCOS--     --CH.sub.2 --     264      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCOS--     --(CH.sub.2).sub.2 --     265      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOS--     --(CH.sub.2).sub.2 --     266      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOS--     --(CH.sub.2).sub.2 --     267      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCOS--     --(CH.sub.2).sub.2 --     268      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCOS--     --(CH.sub.2).sub.3 --     269      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOS--     --(CH.sub.2).sub.3 --     270      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOS--     --(CH.sub.2).sub.3 --     271      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOS--     --(CH.sub.2).sub.4 --     272      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOS--     --(CH.sub.2).sub.5 --     273      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOS--     --(CH.sub.2).sub.6 --     274      CH.sub.3 (CH.sub.2).sub.15 --                          --OCONH--     --CH.sub.2 --     275      CH.sub.3 (CH.sub.2).sub.17 --                          --OCONH--     --CH.sub.2 --     276      CH.sub.3 (CH.sub.2).sub.15 --                          --OCONH--     --(CH.sub.2).sub.2 --     277      CH.sub.3 (CH.sub.2).sub.17 --                          --OCONH--     --(CH.sub.2).sub.2 --     278      CH.sub.3 (CH.sub.2).sub.17 --                          --OCONH--     --(CH.sub.2).sub.3 --     279      CH.sub.3 (CH.sub.2).sub.17 --                          --OCONH--     --(CH.sub.2).sub.4 --     280      CH.sub.3 (CH.sub.2).sub.17 --                          --OCONH--     --(CH.sub.2).sub.5 --     281      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCOCONH--  --CH.sub.2 --     282      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCOCONH--  --CH.sub.2 --     283      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOCONH--  --CH.sub.2 --     284      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOCONH--  --CH.sub.2 --     285      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCOCONH--  --(CH.sub.2).sub.2 --     286      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOCONH--  --(CH.sub.2).sub.2 --     287      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOCONH--  --(CH.sub.2).sub.2 --     288      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCOCONH--  --(CH.sub.2).sub.2 --     289      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCOCONH--  --(CH.sub.2).sub.3 --     290      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCOCONH--  --(CH.sub.2).sub.3 --     291      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOCONH--  --(CH.sub.2).sub.3 --     292      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOCONH--  --(CH.sub.2).sub.4 --     293      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOCONH--  --(CH.sub.2).sub.5 --     294      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCOCONH--  --(CH.sub.2).sub.6 --     295      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONHNH--  --CH.sub.2 --     296      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONHNH--  --CH.sub.2 --     297      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNH--  --CH.sub.2 --     298      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCONHNH--  --CH.sub.2 --     299      CH.sub.3 (CH.sub.2).sub.13 --                          --NHCONHNH--  --(CH.sub.2).sub.2 --     300      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONHNH--  --(CH.sub.2).sub.2 --     301      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNH--  --(CH.sub.2).sub.2 --     302      CH.sub.3 (CH.sub.2).sub.21 --                          --NHCONHNH--  --(CH.sub.2).sub.2 --     303      CH.sub.3 (CH.sub.2).sub.11 --                          --NHCONHNH--  --(CH.sub.2).sub.3 --     304      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONHNH--  --(CH.sub.2).sub.3 --     305      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNH--  --(CH.sub.2).sub.3 --     306      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNH--  --(CH.sub.2).sub.4 --     307      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNH--  --(CH.sub.2).sub.5 --     308      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNH--  --(CH.sub.2).sub.6 --     309      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONHNHCO--                                        --CH.sub.2 --     310      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNHCO--                                        --CH.sub.2 --     311      CH.sub.3 (CH.sub.2).sub.15 --                          --NHCONHNHCO--                                        --(CH.sub.2).sub.2 --     312      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNHCO--                                        --(CH.sub.2).sub.2 --     313      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNHCO--                                        --(CH.sub.2).sub.3 --     314      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNHCO--                                        --(CH.sub.2).sub.4 --     315      CH.sub.3 (CH.sub.2).sub.17 --                          --NHCONHNHCO--                                        --(CH.sub.2).sub.5 --     316      CH.sub.3 (CH.sub.2).sub.11 --                          --OCO--       --CH.sub.2 --     317      CH.sub.3 (CH.sub.2).sub.13 --                          --OCO--       --CH.sub.2 --     318      CH.sub.3 (CH.sub.2).sub.15 --                          --OCO--       --CH.sub.2 --     319      CH.sub.3 (CH.sub.2).sub.17 --                          --OCO--       --CH.sub.2 --     320      CH.sub.3 (CH.sub.2).sub.13 --                          --OCO--       --(CH.sub.2).sub.2 --     321      CH.sub.3 (CH.sub.2).sub.15 --                          --OCO--       --(CH.sub.2).sub.2 --     322      CH.sub.3 (CH.sub.2).sub.17 --                          --OCO--       --(CH.sub.2).sub.2 --     323      CH.sub.3 (CH.sub.2).sub.21 --                          --OCO--       --(CH.sub.2).sub.2 --     324      CH.sub.3 (CH.sub.2).sub.11 --                          --OCO--       --(CH.sub.2).sub.3 --     325      CH.sub.3 (CH.sub.2).sub.15 --                          --OCO--       --(CH.sub.2).sub.3 --     326      CH.sub.3 (CH.sub.2).sub.17 --                          --OCO--       --(CH.sub.2).sub.3 --     327      CH.sub.3 (CH.sub.2).sub.17 --                          --OCO--       --(CH.sub.2).sub.4 --     328      CH.sub.3 (CH.sub.2).sub.17 --                          --OCO--       --(CH.sub.2).sub.5 --     329      CH.sub.3 (CH.sub.2).sub.17 --                          --OCO--       --(CH.sub.2).sub.6 --     330      CH.sub.3 (CH.sub.2).sub.13 --                          --OCOO--      --CH.sub.2 --     331      CH.sub.3 (CH.sub.2).sub.15 --                          --OCOO--      --CH.sub.2 --     332      CH.sub.3 (CH.sub.2).sub.17 --                          --OCOO--      --CH.sub.2 --     333      CH.sub.3 (CH.sub.2).sub.21 --                          --OCOO--      --CH.sub.2 --     334      CH.sub.3 (CH.sub.2).sub.13 --                          --OCOO--      --(CH.sub.2).sub.2 --     335      CH.sub.3 (CH.sub.2).sub.15 --                          --OCOO--      --(CH.sub.2).sub.2 --     336      CH.sub.3 (CH.sub.2).sub.17 --                          --OCOO--      --(CH.sub.2).sub.2 --     337      CH.sub.3 (CH.sub.2).sub.21 --                          --OCOO--      --(CH.sub.2).sub.2 --     335      CH.sub.3 (CH.sub.2).sub.11 --                          --OCOO--      --(CH.sub.2).sub.3 --     339      CH.sub.3 (CH.sub.2).sub.15 --                          --OCOO--      --(CH.sub.2).sub.3 --     340      CH.sub.3 (CH.sub.2).sub.17 --                          --OCOO--      --(CH.sub.2).sub.3 --     341      CH.sub.3 (CH.sub.2).sub.17 --                          --OCOO--      --(CH.sub.2).sub.4 --     342      CH.sub.3 (CH.sub.2).sub.17 --                          --OCOO--      --(CH.sub.2).sub.5 --     343      CH.sub.3 (CH.sub.2).sub.17 --                          --OCOO--      --(CH.sub.2).sub.6 --     344      CH.sub.3 (CH.sub.2).sub.15 --                          --SCO--       --CH.sub.2 --     345      CH.sub.3 (CH.sub.2).sub.17 --                          --SCO--       --CH.sub.2 --     346      CH.sub.3 (CH.sub.2).sub.15 --                          --SCO--       --(CH.sub.2).sub.2 --     347      CH.sub.3 (CH.sub.2).sub.17 --                          --SCO--       --(CH.sub.2).sub.2 --     348      CH.sub.3 (CH.sub.2).sub.17 --                          --SCO--       --(CH.sub.2).sub.3 --     349      CH.sub.3 (CH.sub.2).sub.17 --                          --SCO--       --(CH.sub.2).sub.4 --     350      CH.sub.3 (CH.sub.2).sub.17 --                          --SCO--       --(CH.sub.2).sub.5 --     351      CH.sub.3 (CH.sub.2).sub.7 --                          --NH--        --CH.sub.2 --     352      CH.sub.3 (CH.sub.2).sub.11 --                          --NH--        --CH.sub.2 --     353      CH.sub.3 (CH.sub.2).sub.13 --                          --NH--        --CH.sub.2 --     354      CH.sub.3 (CH.sub.2).sub.15 --                          --NH--        --CH.sub.2 --     355      CH.sub.3 (CH.sub.2).sub.17 --                          --NH--        --CH.sub.2 --     356      CH.sub.3 (CH.sub.2).sub.19 --                          --NH--        --CH.sub.2 --     357      CH.sub.3 (CH.sub.2).sub.21 --                          --NH--        --CH.sub.2 --     358      CH.sub.3 (CH.sub.2).sub.7 --                          --NH--        --(CH.sub.2).sub.2 --     359      CH.sub.3 (CH.sub.2).sub.11 --                          --NH--        --(CH.sub.2).sub.2 --     360      CH.sub.3 (CH.sub.2).sub.13 --                          --NH--        --(CH.sub.2).sub.2 --     361      CH.sub.3 (CH.sub.2).sub.15 --                          --NH--        --(CH.sub.2).sub.2 --     362      CH.sub.3 (CH.sub.2).sub.17 --                          --NH--        --(CH.sub.2).sub.2 --     363      CH.sub.3 (CH.sub.2).sub.19 --                          --NH--        --(CH.sub.2).sub.2 --     364      CH.sub.3 (CH.sub.2).sub.21 --                          --NH--        --(CH.sub.2).sub.2 --     365      CH.sub.3 (CH.sub.2).sub.7 --                          --NH--        --(CH.sub.2).sub.3 --     366      CH.sub.3 (CH.sub.2).sub.11 --                          --NH--        --(CH.sub.2).sub.3 --     367      CH.sub.3 (CH.sub.2).sub.13 --                          --NH--        --(CH.sub.2).sub.3 --     368      CH.sub.3 (CH.sub.2).sub.15 --                          --NH--        --(CH.sub.2).sub.3 --     369      CH.sub.3 (CH.sub.2).sub.17 --                          --NH--        --(CH.sub.2).sub.3 --     370      CH.sub.3 (CH.sub.2).sub.19 --                          --NH--        --(CH.sub.2).sub.3 --     371      CH.sub.3 (CH.sub.2).sub.21 --                          --NH--        --(CH.sub.2).sub.3 --     372      CH.sub.3 (CH.sub.2).sub.7 --                          --NH--        --(CH.sub.2).sub.4 --     373      CH.sub.3 (CH.sub.2).sub.11 --                          --NH--        --(CH.sub.2).sub.4 --     374      CH.sub.3 (CH.sub.2).sub.13 --                          --NH--        --(CH.sub.2).sub.4 --     375      CH.sub.3 (CH.sub.2).sub.15 --                          --NH--        --(CH.sub.2).sub.4 --     376      CH.sub.3 (CH.sub.2).sub.17 --                          --NH--        --(CH.sub.2).sub.4 --     377      CH.sub.3 (CH.sub.2).sub.19 --                          --NH--        --(CH.sub.2).sub.4 --     378      CH.sub.3 (CH.sub.2).sub.21 --                          --NH--        --(CH.sub.2).sub.4 --     379      CH.sub.3 (CH.sub.2).sub.11 --                          --NH--        --(CH.sub.2).sub.5 --     380      CH.sub.3 (CH.sub.2).sub.13 --                          --NH--        --(CH.sub.2).sub.5 --     381      CH.sub.3 (CH.sub.2).sub.15 --                          --NH--        --(CH.sub.2).sub.5 --     382      CH.sub.3 (CH.sub.2).sub.17 --                          --NH--        --(CH.sub.2).sub.5 --     383      CH.sub.3 (CH.sub.2).sub.11 --                          --NH--        --(CH.sub.2).sub.6 --     384      CH.sub.3 (CH.sub.2).sub.13 --                          --NH--        --(CH.sub.2).sub.6 --     385      CH.sub.3 (CH.sub.2).sub.17 --                          --NH--        --(CH.sub.2).sub.6 --     386      CH.sub.3 (CH.sub.2).sub.7 --                          --O--         --CH.sub.2 --     387      CH.sub.3 (CH.sub.2).sub.11 --                          --O--         --CH.sub.2 --     388      CH.sub.3 (CH.sub.2).sub.13 --                          --O--         --CH.sub.2 --     389      CH.sub.3 (CH.sub.2).sub.15 --                          --O--         --CH.sub.2 --     390      CH.sub.3 (CH.sub.2).sub.17 --                          --O--         --CH.sub.2 --     391      CH.sub.3 (CH.sub.2).sub.19 --                          --O--         --CH.sub.2 --     392      CH.sub.3 (CH.sub.2).sub.21 --                          --O--         --CH.sub.2 --     393      CH.sub.3 (CH.sub.2).sub.7 --                          --O--         --(CH.sub.2).sub.2 --     394      CH.sub.3 (CH.sub.2).sub.11 --                          --O--         --(CH.sub.2).sub.2 --     395      CH.sub.3 (CH.sub.2).sub.13 --                          --O--         --(CH.sub.2).sub.2 --     396      CH.sub.3 (CH.sub.2).sub.15 --                          --O--         --(CH.sub.2).sub.2 --     397      CH.sub.3 (CH.sub.2).sub.17 --                          --O--         --(CH.sub.2).sub.2 --     398      CH.sub.3 (CH.sub.2).sub.19 --                          --O--         --(CH.sub.2).sub.2 --     399      CH.sub.3 (CH.sub.2).sub.21 --                          --O--         --(CH.sub.2).sub.2 --     400      CH.sub.3 (CH.sub.2).sub.7 --                          --O--         --(CH.sub.2).sub.3 --     401      CH.sub.3 (CH.sub.2).sub.11 --                          --O--         --(CH.sub.2).sub.3 --     402      CH.sub.3 (CH.sub.2).sub.13 --                          --O--         --(CH.sub.2).sub.3 --     403      CH.sub.3 (CH.sub.2).sub.15 --                          --O--         --(CH.sub.2).sub.3 --     404      CH.sub.3 (CH.sub.2).sub.17 --                          --O--         --(CH.sub.2).sub.3 --     405      CH.sub.3 (CH.sub.2).sub.19 --                          --O--         --(CH.sub.2).sub.3 --     406      CH.sub.3 (CH.sub.2).sub.21 --                          --O--         --(CH.sub.2).sub.3 --     407      CH.sub.3 (CH.sub.2).sub.7 --                          --O--         --(CH.sub.2).sub.4 --     408      CH.sub.3 (CH.sub.2).sub.11 --                          --O--         --(CH.sub.2).sub.4 --     409      CH.sub.3 (CH.sub.2).sub.13 --                          --O--         --(CH.sub.2).sub.4 --     410      CH.sub.3 (CH.sub.2).sub.15 --                          --O--         --(CH.sub.2).sub.4 --     411      CH.sub.3 (CH.sub.2).sub.17 --                          --O--         --(CH.sub.2).sub.4 --     412      CH.sub.3 (CH.sub.2).sub.19 --                          --O--         --(CH.sub.2).sub.4 --     413      CH.sub.3 (CH.sub.2).sub.21 --                          --O--         --(CH.sub.2).sub.4 --     414      CH.sub.3 (CH.sub.2).sub.11 --                          --O--         --(CH.sub.2).sub.5 --     415      CH.sub.3 (CH.sub.2).sub.13 --                          --O--         --(CH.sub.2).sub.5 --     416      CH.sub.3 (CH.sub.2).sub.15 --                          --O--         --(CH.sub.2).sub.5 --     417      CH.sub.3 (CH.sub.2).sub.17 --                          --O--         --(CH.sub.2).sub.5 --     418      CH.sub.3 (CH.sub.2).sub.11 --                          --O--         --(CH.sub.2).sub.6 --     419      CH.sub.3 (CH.sub.2).sub.13 --                          --O--         --(CH.sub.2).sub.6 --     420      CH.sub.3 (CH.sub.2).sub.17 --                          --O--         --(CH.sub.2).sub.6 --     421      CH.sub.3 (CH.sub.2).sub.7 --                          --S--         --CH.sub.2 --     422      CH.sub.3 (CH.sub.2).sub.11 --                          --S--         --CH.sub.2 --     423      CH.sub.3 (CH.sub.2).sub.13 --                          --S--         --CH.sub.2 --     424      CH.sub.3 (CH.sub.2).sub.15 --                          --S--         --CH.sub.2 --     425      CH.sub.3 (CH.sub.2).sub.17 --                          --S--         --CH.sub.2 --     426      CH.sub.3 (CH.sub.2).sub.19 --                          --S--         --CH.sub.2 --     427      CH.sub.3 (CH.sub.2).sub.21 --                          --S--         --CH.sub.2 --     425      CH.sub.3 (CH.sub.2).sub.7 --                          --S--         --(CH.sub.2).sub.2 --     429      CH.sub.3 (CH.sub.2).sub.11 --                          --S--         --(CH.sub.2).sub.2 --     430      CH.sub.3 (CH.sub.2).sub.13 --                          --S--         --(CH.sub.2).sub.2 --     431      CH.sub.3 (CH.sub.2).sub.15 --                          --S--         --(CH.sub.2).sub.2 --     432      CH.sub.3 (CH.sub.2).sub.17 --                          --S--         --(CH.sub.2).sub.2 --     433      CH.sub.3 (CH.sub.2).sub.19 --                          --S--         --(CH.sub.2).sub.2 --     434      CH.sub.3 (CH.sub.2).sub.21 --                          --S--         --(CH.sub.2).sub.2 --     435      CH.sub.3 (CH.sub.2).sub.7 --                          --S--         --(CH.sub.2).sub.3 --     436      CH.sub.3 (CH.sub.2).sub.11 --                          --S--         --(CH.sub.2).sub.3 --     437      CH.sub.3 (CH.sub.2).sub.13 --                          --S--         --(CH.sub.2).sub.3 --     438      CH.sub.3 (CH.sub.2).sub.15 --                          --S--         --(CH.sub.2).sub.3 --     439      CH.sub.3 (CH.sub.2).sub.17 --                          --S--         --(CH.sub.2).sub.3 --     440      CH.sub.3 (CH.sub.2).sub.19 --                          --S--         --(CH.sub.2).sub.3 --     441      CH.sub.3 (CH.sub.2).sub.21 --                          --S--         --(CH.sub.2).sub.3 --     442      CH.sub.3 (CH.sub.2).sub.7 --                          --S--         --(CH.sub.2).sub.4 --     443      CH.sub.3 (CH.sub.2).sub.11 --                          --S--         --(CH.sub.2).sub.4 --     444      CH.sub.3 (CH.sub.2).sub.13 --                          --S--         --(CH.sub.2).sub.4 --     445      CH.sub.3 (CH.sub.2).sub.15 --                          --S--         --(CH.sub.2).sub.4 --     446      CH.sub.3 (CH.sub.2).sub.17 --                          --S--         --(CH.sub.2).sub.4 --     447      CH.sub.3 (CH.sub.2).sub.19 --                          --S--         --(CH.sub.2).sub.4 --     448      CH.sub.3 (CH.sub.2).sub.21 --                          --S--         --(CH.sub.2).sub.4 --     449      CH.sub.3 (CH.sub.2).sub.11 --                          --S--         --(CH.sub.2).sub.5 --     450      CH.sub.3 (CH.sub.2).sub.13 --                          --S--         --(CH.sub.2).sub.5 --     451      CH.sub.3 (CH.sub.2).sub.15 --                          --S--         --(CH.sub.2).sub.5 --     452      CH.sub.3 (CH.sub.2).sub.17 --                          --S--         --(CH.sub.2).sub.5 --     453      CH.sub.3 (CH.sub.2).sub.11 --                          --S--         --(CH.sub.2).sub.6 --     454      CH.sub.3 (CH.sub.2).sub.13 --                          --S--         --(CH.sub.2).sub.6 --     455      CH.sub.3 (CH.sub.2).sub.17 --                          --S--         --(CH.sub.2).sub.6 --     456      CH.sub.3 (CH.sub.2).sub.7 --                          --CH═N--  --CH.sub.2 --     457      CH.sub.3 (CH.sub.2).sub.11 --                          --NH═C--  --CH.sub.2 --     458      CH.sub.3 (CH.sub.2).sub.13 --                          --CH═N--  --CH.sub.2 --     459      CH.sub.3 (CH.sub.2).sub.15 --                          --NH═C--  --CH.sub.2 --     460      CH.sub.3 (CH.sub.2).sub.17 --                          --C═NH--  --CH.sub.2 --     461      CH.sub.3 (CH.sub.2).sub.19 --                          --CH═N--  --CH.sub.2 --     462      CH.sub.3 (CH.sub.2).sub.21 --                          --NH═C--  --CH.sub.2 --     463      CH.sub.3 (CH.sub.2).sub.7 --                          --CH═N--  --(CH.sub.2).sub.2 --     464      CH.sub.3 (CH.sub.2).sub.11 --                          --NH═C--  --(CH.sub.2).sub.2 --     465      CH.sub.3 (CH.sub.2).sub.13 --                          --C═NH--  --(CH.sub.2).sub.2 --     466      CH.sub.3 (CH.sub.2).sub.15 --                          --CH═N--  --(CH.sub.2).sub.2 --     467      CH.sub.3 (CH.sub.2).sub.17 --                          --NH═C--  --(CH.sub.2).sub.2 --     468      CH.sub.3 (CH.sub.2).sub.19 --                          --CH═N--  --(CH.sub.2).sub.2 --     469      CH.sub.3 (CH.sub.2).sub.21 --                          --NH═C--  --(CH.sub.2).sub.2 --     470      CH.sub.3 (CH.sub.2).sub.7 --                          --C═NH--  --(CH.sub.2).sub.3 --     471      CH.sub.3 (CH.sub.2).sub.11 --                          --CH═N--  --(CH.sub.2).sub.3 --     472      CH.sub.3 (CH.sub.2).sub.13 --                          --NH═C--  --(CH.sub.2).sub.3 --     473      CH.sub.3 (CH.sub.2).sub.15 --                          --CH═N--  --(CH.sub.2).sub.3 --     474      CH.sub.3 (CH.sub.2).sub.17 --                          --NH═C--  --(CH.sub.2).sub.3 --     475      CH.sub.3 (CH.sub.2).sub.19 --                          --C═NH--  --(CH.sub.2).sub.3 --     476      CH.sub.3 (CH.sub.2).sub.21 --                          --CH═N--  --(CH.sub.2).sub.3 --     477      CH.sub.3 (CH.sub.2).sub.7 --                          --NH═C--  --(CH.sub.2).sub.4 --     478      CH.sub.3 (CH.sub.2).sub.11 --                          --CH═N--  --(CH.sub.2).sub.4 --     479      CH.sub.3 (CH.sub.2).sub.13 --                          --NH═C--  --(CH.sub.2).sub.4 --     480      CH.sub.3 (CH.sub.2).sub.15 --                          --C═NH--  --(CH.sub.2).sub.4 --     481      CH.sub.3 (CH.sub.2).sub.17 --                          --CH═N--  --(CH.sub.2).sub.4 --     482      CH.sub.3 (CH.sub.2).sub.19 --                          --NH═C--  --(CH.sub.2).sub.4 --     483      CH.sub.3 (CH.sub.2).sub.21 --                          --CH═N--  --(CH.sub.2).sub.4 --     484      CH.sub.3 (CH.sub.2).sub.11 --                          --NH═C--  --(CH.sub.2).sub.5 --     485      CH.sub.3 (CH.sub.2).sub.13 --                          --C═NH--  --(CH.sub.2).sub.5 --     486      CH.sub.3 (CH.sub.2).sub.15 --                          --CH═N--  --(CH.sub.2).sub.5 --     487      CH.sub.3 (CH.sub.2).sub.17 --                          --NH═C--  --(CH.sub.2).sub.5 --     488      CH.sub.3 (CH.sub.2).sub.11 --                          --CH═N--  --(CH.sub.2).sub.6 --     489      CH.sub.3 (CH.sub.2).sub.13 --                          --NH═C--  --(CH.sub.2).sub.6 --     490      CH.sub.3 (CH.sub.2).sub.17 --                          --C═NH--  --(CH.sub.2).sub.6 --     ______________________________________

Also, in the above formula (1), more than two X (i.e., a divalent group having at least one hetero atom) may be present via a hydrocarbon group such as alkylene group. That is, the carboxylic acid compound of the present invention may have a structure in which X in the above formula has a structure of:

    --Y--(R.sub.3 --Y').sub.r --

wherein Y and Y' represents, respectively, a divalent group having at least one hetero atom,

R₃ represents a divalent hydrocarbon group whose principle chain may contain a non-limiting number of carbon atoms, a portion of which may form aromatic ring(s), and

_(r) represents an integer between 1 and 4 (note that when _(r) is more than 2, R₃ and Y', respectively, may be the same or different.

Examples of preferable compounds of the above include compounds having the following formulae (3) to (6):

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.2 --COOH                  (3)

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.2 --COOH   (4)

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.2 --COOH(5)

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.3 "'--Y""--R.sub.2 --COOH                                   (6)

wherein R₃ ', R₃ " and R₃ "', respectively, has the same definition as R₃ and they can be the same or different, and

Y", Y"' and Y"" has the same definition as Y, and they can be the same or different.

Examples of the above compounds wherein R₃, R₃ ', R₃ " and R₃ "', respectively, is an alkylene group may be as follows:

    CH.sub.3 (CH.sub.2).sub.m-1 --Y--(CH.sub.2).sub.w --Y'--(CH.sub.2).sub.n --COOH                                                    (7)

    CH.sub.3 (CH.sub.2).sub.m-1 --Y--(CH.sub.2).sub.w --Y'--(CH.sub.2).sub.x --Y"--(CH.sub.2).sub.n --COOH                             (8)

    CH.sub.3 (CH.sub.2).sub.m-1 --Y--(CH.sub.2).sub.w --Y'--(CH.sub.2).sub.x --Y"--(CH.sub.2).sub.y --Y"'--(CH.sub.2).sub.n --COOH     (9)

    CH.sub.3 (CH.sub.2).sub.m-1 --Y--(CH.sub.2).sub.w --Y'--(CH.sub.2).sub.x --Y"--(CH.sub.2).sub.y --Y"'--(CH.sub.2).sub.z --Y""--(CH.sub.2).sub.n --COOH                                                    (10)

wherein _(w') x' y and _(z') respectively, represents an integer between zero and 8 preferably but not particularly limited.

Examples of carboxylic acid compound having the above formula (7) according to the present invention are shown in the following Tables 2-1 through 2-5. Although examples of carboxylic acid compounds having the above formulae (8) to (10) are not shown, the same Y, Y', Y", Y"' and Y"" shown in Tables 2-1 through 2-5 may be applied to these compounds. However, they are not by any means to restrict the present invention.

                                      TABLE 2     __________________________________________________________________________     Compound     No.   CH.sub.3 (CH.sub.2).sub.m-1 --                   --Y--    --(CH.sub.2).sub.w --                                  --Y'--   --(CH.sub.2).sub.n --     __________________________________________________________________________     491   CH.sub.3 (CH.sub.2).sub.21 --                   --NH--   --(CH.sub.2).sub.4 --                                  --NHCO-- --CH.sub.2 --     492   CH.sub.3 (CH.sub.2).sub.17 --                   --NH--   --(CH.sub.2).sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     493   CH.sub.3 (CH.sub.2).sub.16 --                   --CO--   --(CH.sub.2).sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     494   CH.sub.3 (CH.sub.2).sub.16 --                   --CO--   --CH.sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     495   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.5 --                                  --NHCO-- --(CH.sub.2).sub.5 --     496   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     497   CH.sub.3 (CH.sub.2).sub.11 --                   --O--    --(CH.sub.2).sub.4 --                                  --NHCO-- --(CH.sub.2).sub.3 --     498   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.3 --                                  --NHCO-- --CH.sub.2 --     499   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.4 --                                  --NHCO-- --CH.sub.2 --     500   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     501   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.5 --                                  --NHCO-- --(CH.sub.2).sub.5 --     502   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCOO--                            --CH.sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     503   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.3 --                                  --NHCO-- --CH.sub.2 --     504   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.4 --                                  --NHCO-- --CH.sub.2 --     505   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     506   CH.sub.3 (CH.sub.2).sub.13 --                   --NHCONH--                            --(CH.sub.2).sub.6 --                                  --NHCO-- --(CH.sub.2).sub.2 --     507   CH.sub.3 (CH.sub.2).sub.13 --                   --NHCONH--                            --(CH.sub.2).sub.4 --                                  --NHCO-- --(CH.sub.2).sub.3 --     508   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.4 --                                  --NHCO-- --CH.sub.2 --     509   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.3 --                                  --NHCO-- --CH.sub.2 --     510   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 NH--                            --(CH.sub.2).sub.3 --                                  --NHCO-- --(CH.sub.2).sub.3 --     511   CH.sub.3 (CH.sub.2).sub.21 --                   --NHCSNH--                            --(CH.sub.2).sub.4 --                                  --NHCO-- --(CH.sub.2).sub.2 --     512   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHCONH--                            --(CH.sub.2).sub.3 --                                  --NHCO-- --(CH.sub.2).sub.3 --     513   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHCO--                            --CH.sub.2 --                                  --NHCO-- --CH.sub.2 --     514   CH.sub.3 (CH.sub.2).sub.16 --                   --COO--  --(CH.sub.2).sub.2 --                                  --NHCO-- --(CH.sub.2).sub.2 --     515   CH.sub.3 (CH.sub.2).sub.20 --                   --COO--  --(CH.sub.2).sub.3 --                                  --NHCO-- --(CH.sub.2).sub.3 --     516   CH.sub.3 (CH.sub.2).sub.16 --                   --COS--  --(CH.sub.2).sub.4 --                                  --NHCO-- --(CH.sub.2).sub.6 --     517   CH.sub.3 (CH.sub.2).sub.15 --                   --CH═N--                            --(CH.sub.2).sub.6 --                                  --NHCO-- --(CH.sub.2).sub.2 --     518   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONHCO--                            --(CH.sub.2).sub.2 --                                  --NHCO-- --CH.sub.2 --     519   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHNHCO--                            --(CH.sub.2).sub.3 --                                  --NHCO-- --(CH.sub.2).sub.5 --     520   CH.sub.3 (CH.sub.2).sub.16 --                   --NHNHCONH--                            --(CH.sub.2).sub.4 --                                  --NHCO-- --CH.sub.2 --     521   CH.sub.3 (CH.sub.2).sub.21 --                   --NH--   --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --CH.sub.2 --     522   CH.sub.3 (CH.sub.2).sub.17 --                   --NH--   --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     523   CH.sub.3 (CH.sub.2).sub.16 --                   --CO--   --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     524   CH.sub.3 (CH.sub.2).sub.16 --                   --CO--   --CH.sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     525   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.5 --                                  --NHCONH--                                           --(CH.sub.2).sub.5 --     526   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     527   CH.sub.3 (CH.sub.2).sub.11 --                   --O--    --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --(CH.sub.2).sub.3 --     528   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --CH.sub.2 --     529   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --CH.sub.2 --     530   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     531   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.5 --                                  --NHCONH--                                           --(CH.sub.2).sub.5 --     532   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCOO--                            --CH.sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     533   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --CH.sub.2 --     534   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --CH.sub.2 --     535   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     536   CH.sub.3 (CH.sub.2).sub.13 --                   --NHCONH--                            --(CH.sub.2).sub.6 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     537   CH.sub.3 (CH.sub.2).sub.13 --                   --NHCONH--                            --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --(CH.sub.2).sub.3 --     538   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --CH.sub.2 --     539   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --CH.sub.2 --     540   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 NH--                            --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --(CH.sub.2).sub.3 --     541   CH.sub.3 (CH.sub.2).sub.21 --                   --NHCSNH--                            --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     542   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHCONH--                            --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --(CH.sub.2).sub.3 --     543   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHCO--                            --CH.sub.2 --                                  --NHCONH--                                           --CH.sub.2 --     544   CH.sub.3 (CH.sub.2).sub.16 --                   --COO--  --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     545   CH.sub.3 (CH.sub.2).sub.20 --                   --COO--  --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --(CH.sub.2).sub.3 --     546   CH.sub.3 (CH.sub.2).sub.16 --                   --COS--  --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --(CH.sub.2).sub.6 --     547   CH.sub.3 (CH.sub.2).sub.15 --                   --CH═N--                            --(CH.sub.2).sub.6 --                                  --NHCONH--                                           --(CH.sub.2).sub.2 --     548   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONHCO--                            --(CH.sub.2).sub.2 --                                  --NHCONH--                                           --CH.sub.2 --     549   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHNHCO--                            --(CH.sub.2).sub.3 --                                  --NHCONH--                                           --(CH.sub.2).sub.5 --     550   CH.sub.3 (CH.sub.2).sub.16 --                   --NHNHCONH--                            --(CH.sub.2).sub.4 --                                  --NHCONH--                                           --CH.sub.2 --     551   CH.sub.3 (CH.sub.2).sub.21 --                   --NH--   --(CH.sub.2).sub.4 --                                  --CONH-- --CH.sub.2 --     552   CH.sub.3 (CH.sub.2).sub.17 --                   --NH--   --(CH.sub.2).sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     553   CH.sub.3 (CH.sub.2).sub.16 --                   --CO--   --(CH.sub.2).sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     554   CH.sub.3 (CH.sub.2).sub.16 --                   --CO--   --CH.sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     555   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.5 --                                  --CONH-- --(CH.sub.2).sub.5 --     556   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     557   CH.sub.3 (CH.sub.2).sub.11 --                   --O--    --(CH.sub.2).sub.4 --                                  --CONH-- --(CH.sub.2).sub.3 --     558   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.3 --                                  --CONH-- --CH.sub.2 --     559   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.4 --                                  --CONH-- --CH.sub.2 --     560   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     561   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.5 --                                  --CONH-- --(CH.sub.2).sub.5 --     562   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCOO--                            --CH.sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     563   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.3 --                                  --CONH-- --CH.sub.2 --     564   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.4 --                                  --CONH-- --CH.sub.2 --     565   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     566   CH.sub.3 (CH.sub.2).sub.13 --                   --NHCONH--                            --(CH.sub.2).sub.6 --                                  --CONH-- --(CH.sub.2).sub.2 --     567   CH.sub.3 (CH.sub.2).sub.13 --                   --NHCONH--                            --(CH.sub.2).sub.4 --                                  --CONH-- --(CH.sub.2).sub.3 --     568   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.4 --                                  --CONH-- --CH.sub.2 --     569   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.3 --                                  --CONH-- --CH.sub.2 --     570   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 NH--                            --(CH.sub.2).sub.3 --                                  --CONH-- --(CH.sub.2).sub.3 --     571   CH.sub.3 (CH.sub.2).sub.21 --                   --NHCSNH--                            --(CH.sub.2).sub.4 --                                  --CONH-- --(CH.sub.2).sub.2 --     572   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHCONH--                            --(CH.sub.2).sub.3 --                                  --CONH-- --(CH.sub.2).sub.3 --     573   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHCO--                            --CH.sub.2 --                                  --CONH-- --CH.sub.2 --     574   CH.sub.3 (CH.sub.2).sub.16 --                   --COO--  --(CH.sub.2).sub.2 --                                  --CONH-- --(CH.sub.2).sub.2 --     575   CH.sub.3 (CH.sub.2).sub.20 --                   --COO--  --(CH.sub.2).sub.3 --                                  --CONH-- --(CH.sub.2).sub.3 --     576   CH.sub.3 (CH.sub.2).sub.16 --                   --COS--  --(CH.sub.2).sub.4 --                                  --CONH-- --(CH.sub.2).sub.6 --     577   CH.sub.3 (CH.sub.2).sub.15 --                   --CH═N--                            --(CH.sub.2).sub.6 --                                  --CONH-- --(CH.sub.2).sub.2 --     578   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONHCO--                            --(CH.sub.2).sub.2 --                                  --CONH-- --CH.sub.2 --     579   CH.sub.3 (CH.sub.2).sub.16 --                   --CONHNHCO--                            --(CH.sub.2).sub.3 --                                  --CONH-- --(CH.sub.2).sub.5 --     580   CH.sub.3 (CH.sub.2).sub.16 --                   --NHNHCONH--                            --(CH.sub.2).sub.4 --                                  --CONH-- --CH.sub.2 --     581   CH.sub.3 (CH.sub.2).sub.21 --                   --O--    --(CH.sub.2).sub.4 --                                  --NHCSNH--                                           --CH.sub.2 --     582   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --(CH.sub.2).sub.2 --                                  --NHCSNH--                                           --(CH.sub.2).sub.2 --     583   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.2 --                                  --NHCSNH--                                           --(CH.sub.2).sub.2 --     584   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --CH.sub.2 --                                  --NHCSNH--                                           --(CH.sub.2).sub.2 --     585   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.5 --                                  --NHCSNH--                                           --(CH.sub.2).sub.5 --     586   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.2 --                                  --NHCSNH--                                           --(CH.sub.2).sub.2 --     587   CH.sub.3 (CH.sub.2).sub.12 --                   --COO--  --(CH.sub.2).sub.4 --                                  --NHCSNH--                                           --(CH.sub.2).sub.3 --     588   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCOO--                            --(CH.sub.2).sub.3 --                                  --NHCSNH--                                           --CH.sub.2 --     589   CH.sub.3 (CH.sub.2).sub.17 --                   --NHSO.sub.2 --                            --(CH.sub.2).sub.4 --                                  --NHCSNH--                                           --CH.sub.2 --     590   CH.sub.3 (CH.sub.2).sub.17 --                   --NHNHCONH--                            --(CH.sub.2).sub.2 --                                  --NHCSNH--                                           --(CH.sub.2).sub.2 --     591   CH.sub.3 (CH.sub.2).sub.17 --                   --O--    --(CH.sub.2).sub.5 --                                  --SO.sub.2 --                                           --(CH.sub.2).sub.5 --     592   CH.sub.3 (CH.sub.2).sub.17 --                   --S--    --CH.sub.2 --                                  --SO.sub.2 --                                           --(CH.sub.2).sub.2 --     593   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.3 --                                  --SO.sub.2 --                                           --CH.sub.2 --     594   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.4 --                                  --SO.sub.2 --                                           --CH.sub.2 --     595   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.2 --                                  --SO.sub.2 --                                           --(CH.sub.2).sub.2 --     596   CH.sub.3 (CH.sub.2).sub.13 --                   --SO.sub.2 --                            --(CH.sub.2).sub.6 --                                  --SO.sub.2 --                                           --(CH.sub.2).sub.2 --     597   CH.sub.3 (CH.sub.2).sub.12 --                   --COO--  --(CH.sub.2).sub.4 --                                  --SO.sub.2 --                                           --(CH.sub.2).sub.3 --     598   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCOO--                            --(CH.sub.2).sub.4 --                                  --SO.sub.2 --                                           --CH.sub.2 --     599   CH.sub.3 (CH.sub.2).sub.17 --                   --NHSO.sub.2 --                            --(CH.sub.2).sub.3 --                                  --SO.sub.2 --                                           --CH.sub.2 --     600   CH.sub.3 (CH.sub.2).sub.17 --                   --NHNHCONH--                            --(CH.sub.2).sub.3 --                                  --SO.sub.2 --                                           --(CH.sub.2).sub.3 --     601   CH.sub.3 (CH.sub.2).sub.21 --                   --O--    --(CH.sub.2).sub.4 --                                  --S--    --(CH.sub.2).sub.2 --     602   CH.sub.3 (CH.sub.2).sub.15 --                   --S--    --(CH.sub.2).sub.3 --                                  --S--    --(CH.sub.2).sub.3 --     603   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --CH.sub.2 --                                  --S--    --CH.sub.2 --     604   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.2 --                                  --S--    --(CH.sub.2).sub.2 --     605   CH.sub.3 (CH.sub.2).sub.20 --                   --CONH-- --(CH.sub.2).sub.3 --                                  --S--    --(CH.sub.2).sub.3 --     606   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.4 --                                  --S--    --(CH.sub.2).sub.6 --     607   CH.sub.3 (CH.sub.2).sub.16 --                   --COO--  --(CH.sub.2).sub.6 --                                  --S--    --(CH.sub.2).sub.2 --     608   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCOO--                            --(CH.sub.2).sub.2 --                                  --S--    --CH.sub.2 --     609   CH.sub.3 (CH.sub.2).sub.17 --                   --NHSO.sub.2 --                            --(CH.sub.2).sub.3 --                                  --S--    --(CH.sub.2).sub.5 --     610   CH.sub.3 (CH.sub.2).sub.17 --                   --NHNHCONH--                            --(CH.sub.2).sub.4 --                                  --S--    --CH.sub.2 --     611   CH.sub.3 (CH.sub.2).sub.21 --                   --S--    --(CH.sub.2).sub.4 --                                  --OCO--  --CH.sub.2 --     612   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.2 --                                  --OCO--  --(CH.sub.2).sub.2 --     613   CH.sub.3 (CH.sub.2).sub.16 --                   --CONH-- --(CH.sub.2).sub.2 --                                  --OCO--  --(CH.sub.2).sub.2 --     614   CH.sub.3 (CH.sub.2).sub.16 --                   --NHCONH--                            --CH.sub.2 --                                  --OCO--  --(CH.sub.2).sub.2 --     615   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.5 --                                  --NHCO2--                                           --(CH.sub.2).sub.5 --     616   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.2 --                                  --NHSO2--                                           --(CH.sub.2).sub.2 --     617   CH.sub.3 (CH.sub.2).sub.11 --                   --NHCO-- --(CH.sub.2).sub.4 --                                  --CO--   --(CH.sub.2).sub.3 --     618   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.3 --                                  --CO--   --CH.sub.2 --     619   CH.sub.3 (CH.sub.2).sub.17 --                   --SO.sub.2 --                            --(CH.sub.2).sub.4 --                                  --O--    --CH.sub.2 --     620   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.2 --                                  --O--    --(CH.sub.2).sub.2 --     621   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.5 --                                  --O--    --(CH.sub.2).sub.5 --     622   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --CH.sub.2 --                                  --CONHCO--                                           --(CH.sub.2).sub.2 --     623   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.3 --                                  --NHCONHCO--                                           --CH.sub.2 --     624   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCONH--                            --(CH.sub.2).sub.4 --                                  --CONHCONH--                                           --CH.sub.2 --     625   CH.sub.3 (CH.sub.2).sub.17 --                   --NHCO-- --(CH.sub.2).sub.2 --                                  --NHNHCONH--                                           --(CH.sub.2).sub.2 --     626   CH.sub.3 (CH.sub.2).sub.13 --                   --OCO--  --(CH.sub.2).sub.6 --                                  --N═CH--                                           --(CH.sub.2).sub.2 --     __________________________________________________________________________

The thermally reversible color forming compounds according to the present invention comprises the above-mentioned color developer and a color producing agent. The color producing agent, as mentioned previously, is an electron donating compound and is a dye precursor (leuco dye) having no color or pale color. The color producing agent that may be used in the present invention is not particularly limited and can be selected from the known color producing agents such as phthalide type compounds, azaphthalide type compounds, fluoran type compounds, phenothiazine type compounds, leuco auramine type compounds and so on. Examples of the color producing agents that may be used in the present invention are as follows: ##STR4## wherein R₁ represents a hydrogen or an alkyl group having 1 to 4 carbon atoms; R₂ represents an alkyl group having 1 to 6 carbon atoms, cycloalkyl group, or phenyl group which may be unsubstituted or substituted by an alkyl group such as methyl and ethyl, an alkoxy group such as methoxy and ethoxy, or a halogen; R₃ represents a hydrogen, an alkyl group having 1 to 2 carbon atoms, an alkoxy group, or a halogen; R₄ represents a hydrogen, methyl group, halogen, or an amino group which may be unsubstituted or substituted by an alkyl group, an aryl group which may be substituted by an alkyl group, a halogen, or an alkoxy group, or an aralkyl group which may be substituted by an alkyl group, a halogen, or an alkoxy group.

Examples of the above-mentioned color producing agents include:

2-anilino-3-methyl-6-diethylaminofluoran,

2-anilino-3-methyl-6-di(n-butylamino)fluoran,

2-anilino-3-methyl-6-(N-n-propyl-N-methylamino)fluoran,

2-anilino-3-methyl-6-(N-isopropyl-N-methylamino)fluoran,

2-anilino-3-methyl-6-(N-isobutyl-N-methylamino)fluoran,

2-anilino-3-methyl-6-(N-n-amyl-N-methylamino)fluoran,

2-anilino-3-methyl-6-(N-sec-butyl-N-methylamino)fluoran,

2-anilino-3-methyl-6-(N-n-amyl-N-ethylamino)fluoran,

2-anilino-3-methyl-6-(N-iso-amyl-N-ethylamino)fluoran,

2-anilino-3-methyl-6-(N-n-propyl-N-isopropylamino)fluoran,

2-anilino-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran,

2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran,

2-anilino-3-methyl-6-(N-methyl-p-toluidino)fluoran,

2-(m-trichloromethylanilino)-3-methyl-6-diethylaminofluoran,

2-(m-trifluoromethylanilino)-3-methyl-6-diethylaminofluoran,

2-(m-trichloromethylanilino)-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran

2-(2,4-dimethylanilino)-3-methyl-6-diethylaminofluoran,

2-(N-ethyl-p-toluidino)-3-methyl-6-(N-ethylanilino)fluoran,

2-(N-ethyl-p-toluidino)-3-methyl-6-(N-propyl-p-toluidino)fluoran,

2-anilino-6-(N-n-hexyl-N-ethylaminofluoran,

2-(o-chloroanilino)-6-diethylaminofluoran,

2-(o-chloroanilino)-6-dibutylaminofluoran,

2-(m-trifluoromethylanilino)-6-diethylaminofluoran,

2-(p-acetylanilino)-6-(N-n-amyl-N-n-butylamino)fluoran,

2-benzylamino-6-(N-ethyl-p-toluidino)fluoran,

2-benzylamino-6-(N-methyl-2,4-dimethylanilino)fluoran,

2-benzylamino-6-(N-ethyl-2,4-dimethylanilino)fluoran,

2-benzylamino-6-(N-methyl-p-toluidino)fluoran,

2-(di-p-methylbenzylamino)-6-(N-ethyl-p-toluidino)fluoran,

2-(α-phenylethylamino)-6-(N-ethyl-p-toluidino)fluoran,

2-methylamino-6-(N-methylanilino)fluoran,

2-methylamino-6-(N-ethylanilino)fluoran,

2-methylamino-6-(N-propylanilino)fluoran,

2-ethylamino-6-(N-methyl-p-toluidino)fluoran,

2-methylamino-6-(N-methyl-2,4-dimethylanilino)fluoran,

2-ethylamino-6-(N-ethyl-2,4-dimethylanilino)fluoran,

2-dimethylamino-6-(N-methylanilino)fluoran,

2-dimethylamino-6-(N-ethylanilino)fluoran,

2-diethylamino-6-(N-methyl-p-toluidino)fluoran,

2-diethylamino-6-(N-ethyl-p-toluidino)fluoran,

2-dipropylamino-6-(N-methylanilino)fluoran,

2-dipropylamino-6-(N-ethylanilino)fluoran,

2-amino-6-(N-methylanilino)fluoran,

2-amino-6-(N-ethylanilino)fluoran,

2-amino-6-(N-propylanilino)fluoran,

2-amino-6-(N-methyl-p-toluidino)fluoran,

2-amino-6-(N-ethyl-p-toluidino)fluoran,

2-amino-6-(N-propyl-p-toluidino)fluoran,

2-amino-6-(N-methyl-p-ethylanilino)fluoran,

2-amino-6-(N-methyl-p-ethylanilino)fluoran,

2-amino-6-(N-ethyl-p-ethylanilino)fluoran,

2-amino-6-(N-propyl-p-ethylanilino)fluoran,

2-amino-6-(N-methyl-2,4-dimethylanilino)fluoran,

2-amino-6-(N-ethyl-2,4-dimethylanilino)fluoran,

2-amino-6-(N-propyl-2,4-dimethylanilino)fluoran,

2-amino-6-(N-methyl-p-chloroanilino)fluoran,

2-amino-6-(N-ethyl-p-chloroanilino)fluoran,

2-amino-6-(N-propyl-p-chloroanilino)fluoran,

2,3-dimethyl-6-dimethylaminofluoran,

3-methyl-6-(N-ethyl-p-toluidino)fluoran,

2-chloro-6-diethylaminofluoran,

2-bromo-6-diethylaminofluoran,

2-chloro-6-dipropylaminofluoran,

3-chloro-6-cyclohexylaminofluoran,

3-bromo-6-cyclohexylaminofluoran,

2-chloro-6-(N-ethyl-N-isoamylamino)fluoran,

2-chloro-3-methyl-6-diethylaminofluoran,

2-anilino-3-chloro-6-diethylaminofluoran,

2-(o-chloroanilino)-3-chloro-6-cyclohexylaminofluoran,

2-(m-trifluoromethylanilino)-3-chloro-6-diethylaminofluoran,

2-(2,3-dichloroanilino)-3-chloro-6-diethylaminofluoran,

1,2-benzo-6-diethylaminofluoran,

1,2-benzo-6-(N-ethyl-N-isoamylamino)fluoran,

1,2-benzo-6-dibutylaminofluoran,

1,2-benzo-6-(N-methyl-N-cyclohexylamino)fluoran,

1,2-benzo-6-(N-ethyl-N-toluidino)fluoran, and so on.

Other examples of the color producing agents which may be preferably used in the present invention include:

2-anilino-3-methyl-6-(N-2-ethoxypropyl-N-ethylamino)fluoran,

2-(p-chloroanilino)-6-(N-n-octylamino)fluoran,

2-(p-chloroanilino)-6-(N-n-palmitylamino)fluoran,

2-(p-chloroanilino)-6-(di-n-octylamino)fluoran,

2-benzoylamino-6-(N-ethyl-p-toluidino)fluoran,

2-(o-methoxybenzoylamino)-6-(N-methyl-p-toluidino)fluoran,

2-dibenzylamino-4-methyl-6-diethylamino)fluoran,

2-dibenzylamino-4-methoxy-6-(N-methyl-p-toluidino)fluoran,

2-dibenzylamino-4-methyl-6-(N-ethyl-p-toluidino)fluoran,

2-(α-phenylethylamino)-4-methyl-6-diethylaminofluoran,

2-(p-toluidino)-3-(t-butyl)-6-(N-methyl-p-toluidino)fluoran,

2-(o-methoxycarbonylamino)-6-diethylaminofluoran,

2-acetylamino-6-(N-methyl-p-toluidino)fluoran,

3-diethylamino-6-(m-trifluoromethylanilino)fluoran,

4-methoxy-6-(N-ethyl-p-toluidino)fluoran,

2-ethoxyethylamino-3-chloro-6-dibutylaminofluoran,

2-dibenzylamino-4-chloro-6-(N-ethyl-p-toluidino)fluoran,

2-(α-phenylethylamino)-4-chloro-6-diethylaminofluoran,

2-(N-benzyl-p-trifluoromethylanilino)-4-chloro-6-diethylaminofluoran,

2-anilino-3-methyl-6-pyrrolidinofluoran,

2-anilino-3-chloro-6-pyrrolidinofluoran,

2-anilino-3-methyl-6-(N-ethyl-N-tetrahydrofurfurylamino)fluoran,

2-mesidino-4',5'-benzo-6-diethylaminofluoran,

2-(m-trifluoromethylanilino)-3-methyl-6-pyrrolidinofluoran,

2-(α-naphtylamino)-3,4-benzo-4'-bromo-6-(N-benzyl-N-cyclohexylamino)fluoran,

2-piperidino-6-diethylaminofluoran,

2-(N-n-propyl-p-trifluoromethylanilino)-6-morphorinofluoran,

2-(di-N-p-chlorophenyl-methylamino)-6-pyrrolidinofluoran,

2-(N-n-propyl-m-trifluoromethylanilino)-6-morphorinofluoran,

1,2-benzo-6-(N-ethyl-N-n-octylamino)fluoran,

1,2-benzo-6-diallylamino)fluoran,

1,2-benzo-6-(N-ethoxyethyl-N-ethylamino)fluoran, benzoleuco-methylene blue,

2- 3,6-bis(diethylamino)!-6-(o-chloroanilino)xanthyl benzoic acid lactam,

2- 3,6-diethylamino!-9-(o-chloroanilino)xanthyl benzoic acid lactam,

3,3-bis(p-dimethylaminophenyl)-phthalide,

3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (Crystal violet lacton),

3,3-bis-(p-dimethylaminophenyl)-6-diethylaminophthalide,

3,3-bis-(p-dimethylaminophenyl)-6-chlorophthalide,

3,3-bis-(p-dibutylaminophenyl)phthalide,

3-(2-methoxy-4-dimethylaminophenyl)-3-(2-hydroxy-4,5-dichlorophenyl)phthalide,

3-(2-hydroxy-4-dimethylaminophenyl)-3-(2-methoxy-5-chlorophenyl)phthalide,

3-(2-hydroxy-4-dimethoxyaminophenyl)-3-(2-methoxy-5-chlorophenyl)phthalide,

3-(2-hydroxy-4-dimethylaminophenyl)-3-(2-methoxy-5-nitrophenyl)phthalide,

3-(2-hydroxy-4-diethylaminophenyl)-3-(2-methoxy-5-methylphenyl)phthalide,

3-(2-methoxy-4-dimethylaminophenyl)-3-(2-hydroxy-4-chloro-5-methoxyphenyl)phthalide,

3,6-bis(dimethylamino)fluorenespiro(9,3')-6'-dimethylaminophthalide,

3-(1-ethyl-2-methylindole-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,

3-(1-octyl-2-methylindole-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,

3-(1-ethyl-2-methylindole-3-yl)-3-(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide,

3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide,

3,3-bis(2-ethoxy-4-diethylaminophenyl)-7-azaphthalide,

6'-chloro-8'-methoxy-benzoindolino-spiropyran,

6'-bromo-2'-methoxy-benzoindolino-spiropyran, and so on.

The thermally reversible color forming composition according to the present invention has a characteristic in that there are a color forming state and a non-color state depending on a temperature and/or a cooling rate after the composition is heated to a certain temperature.

FIG. 1 is a graph showing the relationship between a color density and a temperature of the thermally reversible color forming composition according to the present invention. As shown in FIG. 1, by heating the composition in a non-color state, indicated by the letter A, a coloration reaction takes place at a temperature, T₁, at which the composition starts to melt, and the composition enters into a color forming state (liquid) indicated by B. From this color forming state, B, if the composition is cooled rapidly, the colored state of the composition may be maintained even at a room temperature and the composition enters into a color forming state (solid) (i.e., most of the cases it is considered as a solid state) indicated by C. On the other hand, if the composition is cooled gradually from the color forming state B, its color is lost during the temperature decline and the composition reverts to the non-color state A (i.e., the original state) or enters into a state in which its color density is relatively low compared with the color forming state C.

When the temperature of the composition is increased again from the color forming state C, a color deletion of the composition starts at a temperature, T₂, which is a temperature lower than T₁, as indicated by a dotted line (from D to E), and if the temperature is lowered from the point E, the composition reverts to the non-color state A (the original state). Thus, the thermally reversible color forming composition according to the present invention may have either a colored state or a non-colored state when it is in a solid state, depending on the cooling rate from the melting liquid state.

The actual color forming temperature and color deletion temperature, respectively, varies depending on the combination of the color producing agent and the color developer actually used. Thus, a suitable combination of the color producing agent and the color developer may be selected according to the desired temperature for color formation and/or color deletion. Also, the color density of the composition in the color forming state (liquid) and that of the composition in the color forming state (solid) are not always the same and may be different depending on such factors as the combination of the color producing agent and the color developer, etc.

In the color forming state C, the molecules of the color producing agent and those of the color developer are mixed in a state (solid state in most cases, as mentioned above) in which they may be contacted and thus reacted with each other. In this state, the color producing agent and the color developer are cohered and the color forming state is maintained. It is considered that the stability in color formation of the compound according to the present invention depends on the cohesive structure of the color producing agent and the color developer.

In the non-color state A, on the other hand, the color producing agent and the color developer are phase-separated. In this state, molecules of at least one of the color producing agent and the color developer forms domains or is crystallized and it is considered that the composition is stabilized by a separation of the color producing agent from the color developer due to this formation of domains or crystals. According to the present invention, a complete deletion of colors is often performed by the phase separation of the color producing agent from the color developer and the crystallization of the color developer. Both the deletion of color from the color forming state B due to a gradual cooling and the deletion of color from the color forming state C due to a temperature increase followed by a temperature decrease shown in FIG. 1 are caused by the phase-separation of the constituents of the composition or the crystallization of the color developer, both of which involve an alteration of cohesive structure of the molecules.

When the thermally reversible color forming composition of the present invention is used in a thermally reversible recording medium, a colored image may be produced by heating the medium (composition) to a temperature at which the composition of the present invention melts by using a heating means such as a thermal head and then rapidly cooling the medium. The deletion of the produced colored image may be performed by gradually cooling the medium (composition) from a heating state or by heating the medium (composition) to a temperature a little less than the coloration temperature of the composition. This means that the composition is temporarily maintained at a temperature at which the composition is phase-separated or at least one of the color producing agent and the color developer is crystallized. The reason that the medium (composition) is rapidly cooled to form a colored image is that the medium (composition) is not maintained at the phase-separation temperature or the crystallization temperature. The terms "rapid cooling" and "gradual cooling" used in this specification are relative terms and the boundary between the two terms varies depending on a combination of the color producing agent and the color developer used.

Although the ratio of the color producing agent and the color developer present in the thermally reversible color forming composition according to the present invention varies depending on the combination of the two compounds, it is generally 1:0.1-20 and preferably 1:0.2-10. If the amount of the color developer is more or less than the above range, the density of formed color will be decreased and the formation of resulting colored image become problematic.

The thermally reversible recording medium according to the present invention comprises a supporting layer and a recording layer formed on the supporting layer, the recording layer including the above-explained thermally reversible color forming composition as a main component.

Any materials which can support the recording layer can be used as the supporting layer. Such materials include paper, resin film, synthesized paper, metal foil, glass and composite materials made of these.

Any kind of recording layer which contains the thermally reversible color forming composition of the present invention may be used for the thermally reversible recording medium. In general, the recording layer is comprised of a binder resin in which fine particles of a color producing agent and a color developer are dispersed homogeneously. The particles of the color producing agent and the color developer may be particulate particles, however, they are preferably in a composite state. This state of the particles may be achieved by melting or dissolving the color producing agent and the color developer.

The thermally reversible recording medium may be formed by dissolving and dispersing each of the constituents of the recording layer in a respective solvent and then mixing each of the solutions followed by an application of the resulting solution onto a supporting layer and drying, or by mixing each of the constituents of the recording layer in a solvent and then applying the resulting dispersed or dissolved solution onto a supporting layer followed by drying. It is possible to envelop the color producing agent and the color developer in microcapsules.

Additives which may improve a color forming/deleting characteristic or an application characteristic of the recording layer can be added to the thermally reversible recording medium of the present invention if necessary. Examples of such additives include dispersing agents, surfactants, conductivity agents, fillers, lubricants, anti-oxidants, light stabilizers, ultraviolet ray absorbents, color forming stabilizers, and color deletion accelerating agents.

Examples of the binder resin which may be used in the recording layer include poly(vinyl chloride), poly(vinyl acetate), vinyl chloride-vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylate, polymethacrylate, acrylic acid copolymer, maleic acid copolymer, poly(vinyl alcohol), denatured poly(vinyl alcohol), hydroxyethyl cellulose, carboxymethyl cellulose, starch and so on. These binder resins are capable of maintaining a homogeneously dispersed state of each of the constituents of the compositions used for the recording layer even when a thermal energy is applied to the recording layer for recording/deleting an image. Therefore, it is preferable that a resin having an excellent heat resistance capacity is used for the binder resin. Also, it is possible to cross-link a binder resin using, for instance, heat, ultraviolet ray or an electron beam in order to increase its heat resistance.

As mentioned above, the thermally reversible recording medium according to the present invention is basically comprised of a supporting layer and a recording layer formed on the supporting layer. However, the thermally reversible recording medium of the present invention may further include protective layers, adhesive layers, intermediate layers, undercoating layers, backcoating layers, etc., in order to improve its performance as a recording medium.

Now, a surface of the recording layer may be deformed due to heat and/or pressure when a thermal head is used for an image formation. In order to prevent the deformation of the recording layer, it is preferable to provide a protective layer with the recording layer. Examples of the substances which may be used for the protective layer include poly(vinyl alcohol), styrene-maleic anhydride copolymer, carboxy denatured polyethylene, melamine-formaldehyde resin, urea-formaldehyde resin, ultraviolet-cure resin and electron beam-cure resin. Also, it is possible to include additives such as an ultraviolet absorber in the protective layer.

It is preferable to provide an intermediate layer between the recording layer and the protective layer in order to improve adhesibility of the recording layer and the protective layer, to prevent a denaturation of the recording layer due to the application of the protective layer, and to prevent a transfer of the additives contained in the protective layer to the recording layer. Also, it is preferable to use a resin which has a low oxygen permeability for the protective layer and the intermediate layer provided on the recording layer because, in that manner, it is possible to prevent or decrease oxidation of the color producing agent and the color developer contained in the recording layer.

Moreover, it is possible to provide an adiabatic undercoating layer between the supporting layer and the recording layer in order to effectively use the heat applied to the recording medium. The adiabatic undercoating layer may be formed by applying organic or inorganic hollow fine particles using binder resin. Further, it is possible to form an undercoating layer which improves adhesibility of the supporting layer with the recording layer or prevents permeation of recording layer constituents into the supporting layer.

The same resin used for the recording layer may also be used for the intermediate layer and the undercoating layer. Moreover, it is possible to include filler such as calcium carbonate, magnesium carbonate, titanium oxide, silicon oxide, aluminium hydroxide, kaolin and talc in the protective layer, intermediate layer, recording layer and undercoating layer. Other additives such as lubricants and surfactants may also be included in such layers.

In order to produce a colored image using the thermally reversible medium according to the present invention, the medium is heated to a temperature higher than its coloration temperature and then it is rapidly cooled. In practice, when the recording layer is heated for a relatively short time by a thermal head or laser beam, the temperature of a portion of the recording layer may be increased locally to a temperature higher than its coloration temperature and as the application of the heat is stopped, the temperature of the portion of the recording layer is lowered rapidly by diffusion of heat and the colored image is fixed.

In order to delete the formed image, on the other hand, it is necessary to heat the recording layer for a relatively long time using an appropriate heat source and then cool it, or temporarily heat the recording layer at a temperature a little lower than its coloration temperature. That is, if the recording layer is heated for a relatively long time, the temperature of a large area of the recording medium is increased and so it takes a relatively long time to decrease the temperature of it. Thus, the colored image of the recording layer may be deleted during the slow cooling process.

Examples of the above-mentioned heat source that may be used for the slow cooling process of the recording medium include a thermal roller, a thermal stamp and thermal heat. It is possible to use a thermal head for long-time heating. In order to control the temperature of the thermal head, an applied voltage or pulse width for the thermal head may be adjusted so that an applied energy to the recording layer become a little lower than the applied energy which is used during a recording process. By using this method, only a thermal head is necessary for formation/deletion of colored images and thus a so-called overwriting can be performed.

EXAMPLES

The present invention is described in detail using examples hereinafter. Note that the terms "parts" and "%" used in the following examples are based on weight unless otherwise it is noted.

Example 1

A thermally reversible color forming composition according to the present invention was prepared using 2-anilino-3-methyl-6-dibutylaminofluoran as a color producing agent and N'-n-octadecylureido acetic acid as a color developer. The actual preparation procedure of the composition was carried out as follows. First, a mixture of the color producing agent and the color developer (1:3 molar ratio) was ground in a mortar and the powder of the mixture obtained was put on a glass plate with thickness of 1.2 mm. The glass plate was heated to a temperature of 190° C. using a hot plate and the mixture was melted. A cover glass was put on the melted mixture in order to uniformly spread the mixture and the glass plate together with the cover glass was immediately immersed in ice water to rapidly decrease the temperature of the mixture. After that the glass plate was taken out of the water and dried to obtain the composition of the present invention as a colored thin film.

When this colored composition was put on a hot plate heated to a temperature of 120° C., the color of the composition immediately disappeared. After that, when this non-color composition was heated to a temperature of 190° C., the composition turned into a black color.

Thus, it was confirmed that the composition according to the present invention had a reversible color formation/deletion characteristic from the above experiment.

Example 2

The above described procedure used in the Example 1 was repeated except that 3-(N'-n-octadecylureido)propionic acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 3

The above described procedure used in the Example 1 was repeated except that 4-(N'-n-octadecylureido)butyric acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 4

The above described procedure used in the Example 1 was repeated except that 4-(N'-n-octadecylureido)-3-hydroxybutyric acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 5

The above described procedure used in the Example 1 was repeated except that N'-(n-octadecylaminocarbonyl)glycylglycine was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 6

The above described procedure used in the Example 1 was repeated except that N'-(n-octadecylaminocarbonyl)glycylglycylglycine was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 7

The above described procedure used in the Example 1 was repeated except that stearylthioglycolic acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 8

The above described procedure used in the Example 1 was repeated except that stearylthiopropionic acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 9

The above described procedure used in the Example 1 was repeated except that stearoylglycine was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 10

The above described procedure used in the Example 1 was repeated except that stearoylalanine was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 11

The above described procedure used in the Example 1 was repeated except that monodecylamido adipate was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 12

The above described procedure used in the Example 1 was repeated except that monostearylamido adipate was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 13

The above described procedure used in the Example 1 was repeated except that stearylsulfonyl propionic acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 14

The above described procedure used in the Example 1 was repeated except that eicocylsulfonyl propionic acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 15

The above described procedure used in the Example 1 was repeated except that stearylsulfonylglycol acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 16

The above described procedure used in the Example 1 was repeated except that eicosylsulfonyl glycol acid was used as a color developer instead of N'-n-octadecylureido acetic acid. It was confirmed that the composition prepared in this Example also has the reversible color formation/deletion characteristic.

Example 17

The above described procedure used in the Examples 1-16 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used as a color producing agent instead of 2-anilino-3-methyl-6-dibutylaminofluoran. It was confirmed that all the compositions prepared in this Example also has the reversible color formation/deletion characteristic.

Example 18

A solution for applying a thermally reversible recording medium to a recording layer according to the present invention was prepared by a grinding dispersion of the following compounds using a ball mill until a particle size in the range of between 1 and 4 μm was obtained:

    ______________________________________     2-anilino-3-methyl-6-dibutylaminofluoran                                 2     parts     N'-n-octadecylureido acetic acid                                 8     parts     vinyl chloride-vinyl acetate copolymer (Union Carbide Co.,                                 20    parts     VYHH)     methylethylketone           45    parts     toluene                     45    parts     ______________________________________

The solution thus produced was applied to a polyester film of 100 μm thickness using a wired-bar, dried, and a thermally reversible recording medium according to the present invention comprising a recording layer of 6.0 μm thickness was produced.

Example 19

The above described procedure used in the Example 18 was repeated except that 3-(N'-n-octadecylureido)propionic acid was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 20

The above described procedure used in the Example 18 was repeated except that 4-(N'-n-octadecylureido)propion was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 21

The above described procedure used in the Example 18 was repeated except that 4-(N'-n-octadecylureido)-3-hydroxybutyric acid was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 22

The above described procedure used in the Example 18 was repeated except that N'-(n-octadecylaminocarbonyl)glycylglycine was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 23

The above described procedure used in the Example 18 was repeated except that N'-(n-octadecylaminocarbonyl)glycylglycylglycine was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 24

The above described procedure used in the Example 18 was repeated except that stearoylglycine was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 25

The above described procedure used in the Example 18 was repeated except that stearoylalanine was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 26

The above described procedure used in the Example 18 was repeated except that monodecylamido adipate was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 27

The above described procedure used in the Example 18 was repeated except that monostearylamido adipate was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 28

The above described procedure used in the Example 18 was repeated except that stearylsulfonyl propionic acid was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 29

The above described procedure used in the Example 18 was repeated except that eicocylsulfonyl propionic acid was used instead of N'-n-octadecylureido acetic acid and a thermally reversible recording medium of the present invention was prepared.

Example 30

The above described procedure used in the Example 18 was repeated except that 2-anilino-3-methyl-6-diethylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 31

The above described procedure used in the Example 19 was repeated except that 2-anilino-3-methyl-6-diethylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 32

The above described procedure used in the Example 20 was repeated except that 2-anilino-3-methyl-6-diethylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 33

The above described procedure used in the Example 21 was repeated except that 2-anilino-3-methyl-6-diethylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 34

The above described procedure used in the Example 21 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 35

The above described procedure used in the Example 21 was repeated except that 2-(o-chloroanilino)-3-methyl-6-dibutylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 36

The above described procedure used in the Example 22 was repeated except that 2-anilino-3-methyl-6-diethylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 37

The above described procedure used in the Example 23 was repeated except that 2-anilino-3-methyl-6-diethylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and a thermally reversible recording medium of the present invention was prepared.

Example 38

The above described procedure used in the Example 18 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and stearylthioglycol acid was used instead of N'-n-octadecylureido acetic acid, and a thermally reversible recording medium of the present invention was prepared.

Example 39

The above described procedure used in the Example 18 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and eicosylsulfonyl glycol acid was used instead of N'-n-octadecylureido acetic acid, and a thermally reversible recording medium of the present invention was prepared.

Example 40

The above described procedure used in the Example 18 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and stearylthioglycol acid was used instead of N'-n-octadecylureido acetic acid, and a thermally reversible recording medium of the present invention was prepared.

Example 41

The above described procedure used in the Example 18 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and stearylthiopropionic acid was used instead of N'-n-octadecylureido acetic acid, and a thermally reversible recording medium of the present invention was prepared.

Example 42

The above described procedure used in the Example 18 was repeated except that 2-anilino-3-methyl-6-N-ethyl-N-p-tolylaminofluoran was used instead of 2-anilino-3-methyl-6-dibutylaminofluoran and stearoyl-amino-methyl-thiopropionic acid was used instead of N'-n-octadecylureido acetic acid, and a thermally reversible recording medium of the present invention was prepared.

Using the recording media prepared in each of the Examples 18 to 42, a colored image was obtained by carrying out a printing under the following conditions:

Thermal head dot density: 8 dot/mm,

Applied voltage: 13.3 V, and

Applied Pulse width: 1.2 msec.

The optical color density of the colored image on each of the recording media was measured using the Macbeth densitometer RD-914. Then, the color density of each of the colored recording media after heating it for one second using a thermal inclination detector at the temperature shown in the column of "color deleting temperature" (abbreviated as color dele. temp.) in Table 3 for each Example was measured. The results obtained are also shown in Table 3. As can be seen from Table 3, it is clear that the color density of each of the recording medium according to the present invention is decreased to an almost initial color density level of the medium after the one second of heating. Also, it is shown that stable color formation and deletion can be achieved after 10 times of repeated use. Thus, each the recording media according to the present invention is demonstrated to be a thermally reversible recording medium which can perform a fast speed deletion of colored image.

Comparative Example 1

The above described procedure used in the Example 18 was repeated except that eicosyl phosphonic acid was used as a color developer and 2-anilino-3-methyl-6-(N-ethyl-N-p-tolylamino)fluoran was used as a leuco dye, and a recording medium was prepared. Using this recording medium, formation of a colored image (printing) and deletion of the image were performed in the same manner as described in the Example 18. As shown in Table 3, the color of the medium could not be deleted completely after one second of heating. As a matter of fact, it was necessary to heat the medium for one minute to lower its color density to 0.16 which is almost the same as its initial color density.

Comparative Example 2

The above described procedure used in the Example 18 was repeated except that 2-(eicosylthio) succinic acid was used as a color developer, and a recording medium was prepared. Using this recording medium, formation of a colored image (printing) and deletion of the image were performed in the same manner as described in the Example 18. As shown in Table 3, the color of the medium could not be deleted completely after one second of heating. As a matter of fact, it was necessary to heat the medium for ten seconds to lower its color density to 0.21 which is almost the same as its initial color density.

Comparative Example 3

The above described procedure used in the Example 18 was repeated except that α-hydroxyoctadecanoic acid was used as a color developer, and a recording medium was prepared. Using this recording medium, formation of a colored image (printing) and deletion of the image were performed in the same manner as described in the Example 18. As shown in Table 3, the color of the medium could not be deleted completely after one second of heating. As a matter of fact, it was necessary to heat the medium for ten seconds to lower its color density to 0.17 which is almost the same as its initial color density.

Comparative Example 4

The above described procedure used in the Example 18 was repeated except that octadecylmalonic acid was used as a color developer and 2-(o-chloroanilino)-6-dibutylaminofluoran was used as a leuco dye, and a recording medium was prepared. Using this recording medium, formation of a colored image (printing) and deletion of the image were performed in the same manner as described in the Example 18. As shown in Table 3, the color of the medium could not be deleted completely after one second of heating. As a matter of fact, one minute of heating was insufficient for the medium to lower its color density to its initial density.

                  TABLE 3     ______________________________________                    1st. time     Aft. 10 times     color       init.    form.  dele.  form.                                             dele.     dele.       color    color  color  color                                             color     temp.       dens.    dens.  dens.  dens.                                             dens.     ______________________________________     Ex 18   110° C.                     0.09     0.71 0.09   0.70 0.09     Ex 19   110° C.                     0.09     0.82 0.09   0.80 0.10     Ex 20   110° C.                     0.09     0.84 0.09   0.82 0.10     Ex 21   110° C.                     0.10     1.16 0.10   1.15 0.11     Ex 22   120° C.                     0.10     0.72 0.10   0.70 0.11     Ex 23   120° C.                     0.09     0.68 0.09   0.66 0.10     Ex 24   100° C.                     0.11     0.92 0.11   0.88 0.11     Ex 25   100° C.                     0.11     0.86 0.11   0.84 0.11     Ex 26   100° C.                     0.11     0.77 0.11   0.75 0.11     Ex 27   100° C.                     0.11     0.83 0.11   0.80 0.11     Ex 28   100° C.                     0.12     1.05 0.13   1.02 0.13     Ex 29   100° C.                     0.12     1.12 0.12   1.08 0.12     Ex 30   110° C.                     0.10     0.74 0.10   0.72 0.11     Ex 31   110° C.                     0.09     0.85 0.09   0.82 0.10     Ex 32   110° C.                     0.10     0.89 0.10   0.88 0.10     Ex 33   110° C.                     0.11     1.21 0.11   1.20 0.12     Ex 34   110° C.                     0.09     1.10 0.09   1.08 0.10     Ex 35   110° C.                     0.09     1.08 0.09   1.06 0.11     Ex 36   120° C.                     0.10     0.77 0.10   0.74 0.11     Ex 37   120° C.                     0.10     0.71 0.10   0.70 0.11     Ex 38   100° C.                     0.14     1.45 0.15   1.43 0.15     Ex 39   100° C.                     0.14     1.58 0.14   1.52 0.14     Ex 40    60° C.                     0.12     0.82 0.12   0.80 0.12     Ex 41    60° C.                     0.11     0.81 0.11   0.79 0.11     Ex 42    60° C.                     0.12     0.86 0.12   0.84 0.12     CE 1     80° C.                     0.15     1.10 0.45   1.08 0.48     CE 2     70° C.                     0.20     1.46 0.36   1.43 0.38     CE 3     70° C.                     0.16     0.39 0.20   0.38 0.21     CE 4     70° C.                     0.22     1.70 1.29   1.67 1.28     ______________________________________      (Ex = Example,      CE = Comparative Example,      color dele. temp. = color deleting temperature,      init. color dens. = initial color density,      form. color dens. = formed color density,      dele. color dens. = deleted color density)

It is obvious that the present invention is not limited to the above-mentioned embodiments, and variations and modifications may be made without departing from the scope of the present invention. 

What is claimed is:
 1. A thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein said electron-accepting compound isa carboxylic acid compound having the following general formula:

    R.sub.1 --X--R.sub.2 --COOH

wherein, X is selected from the group consisting of ##STR5## R₁ represents a hydrocarbon group which may be substituted and R₂ represents an aliphatic hydrocarbon group, which may be substituted and which has a principle chain containing less than 6 carbon atoms.
 2. A thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein said electron-accepting compound isa carboxylic acid compound having the following general formula:

    R.sub.1 --X--R.sub.2 --COOH

wherein, X represents a divalent group having at least one hetero atom, R₁ represents a hydrocarbon group which is substituted by a substituent selected from the group consisting of a hydroxy group, halogens and alkoxy groups and R₂ represents an aliphatic hydrocarbongroup, which may be substituted and which has a principle chain containing less than 6 carbon atoms.
 3. A thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein said electron-accepting compound isa carboxylic acid compound having the following general formula:

    R.sub.1 --X--R.sub.2 --COOH

wherein, X represents a divalent group having at least one hetero atom, R₁ represents a hydrocarbon group which may be substituted and R₂ represents an aliphatic hydrocarbon group having a principle chain which contains less than 6 carbon atoms and which is substituted by a substituent selected from the group consisting of a hydroxy group and halogens.
 4. The thermally reversible color forming composition as claimed in claim 3, wherein R₁ is substituted by a substituent selected from the group consisting of a hydroxy group, halogens and alkoxy groups.
 5. A thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein said electron-accepting compound isa carboxylic acid compound having the following general formula:

    CH.sub.3 (CH.sub.2).sub.m-1 --X--(CH.sub.2).sub.n --COOH

wherein, X represents a divalent group having at least one hetero atom, m represents an integer between 8 and 22 and n represents an integer between 0 and
 6. 6. A thermally reversible color forming composition comprising an electron-donating chromophoric compound and an electron-accepting compound, by which formation and deletion of a color image may be carried out by adjusting thermal energy applied to the composition, wherein said electron-accepting compound isa carboxylic acid compound having the following general formula:

    R.sub.1 --X--R.sub.2 --COOH

wherein, X may be expressed as:

    --Y--(R.sub.3 --Y').sub.r --

wherein Y and Y' represent, respectively, a divalent group having at least one hetero atom, R₃ represents a divalent hydrocarbon group whose principle chain may contain a non-limiting number of carbon atoms, a portion of which may form aromatic ring(s), and r represents an integer between 1 and 4, and when r is more than 2, R₃ and Y', respectively, may be the same or different.
 7. The thermally reversible color forming composition as claimed in claim 6, wherein said carboxylic acid compound has a general formula selected from the group consisting of the following formulas:

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.2 --COOH

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.2 --COOH

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.2 --COOH,

and

    R.sub.1 --Y--R.sub.3 --Y'--R.sub.3 '--Y"--R.sub.3 "--Y"'--R.sub.3 "'--Y""--R.sub.2 --COOH

wherein R₃ ', R₃ " and R₃ "', respectively, have the same definition as R₃ and R₃ ', R₃ " and R₃ "' may be the same or different from each other, and Y", Y"' and Y"" have the same definition as Y, and Y", Y"' and Y"" may be the same or different from each other.
 8. A thermally reversible recording medium comprising a supporting layer and a recording layer formed on said supporting layer, wherein said recording layer is comprised of the thermally reversible color forming composition as claimed in claim
 1. 9. A thermally reversible recording medium comprising a supporting layer and a recording layer formed on said supporting layer, wherein said recording layer is comprised of the thermally reversible color forming composition as claimed in claim
 5. 10. A thermally reversible recording medium comprising a supporting layer and a recording layer formed on said supporting layer, wherein said recording layer is comprised of the thermally reversible color forming composition as claimed in claim
 6. 11. A thermally reversible recording medium comprising a supporting layer and a recording layer formed on said supporting layer, wherein said recording layer is comprised of the thermally reversible color forming composition as claimed in claim
 7. 